[Improvement] Add prefix `Alignment.` for toString of Alignment (#67860)

* modify: add prefix `Alignment.` for toString of Alignment
diff --git a/packages/flutter/lib/src/painting/alignment.dart b/packages/flutter/lib/src/painting/alignment.dart
index bad49e0..6e7bf58 100644
--- a/packages/flutter/lib/src/painting/alignment.dart
+++ b/packages/flutter/lib/src/painting/alignment.dart
@@ -348,23 +348,23 @@
 
   static String _stringify(double x, double y) {
     if (x == -1.0 && y == -1.0)
-      return 'topLeft';
+      return 'Alignment.topLeft';
     if (x == 0.0 && y == -1.0)
-      return 'topCenter';
+      return 'Alignment.topCenter';
     if (x == 1.0 && y == -1.0)
-      return 'topRight';
+      return 'Alignment.topRight';
     if (x == -1.0 && y == 0.0)
-      return 'centerLeft';
+      return 'Alignment.centerLeft';
     if (x == 0.0 && y == 0.0)
-      return 'center';
+      return 'Alignment.center';
     if (x == 1.0 && y == 0.0)
-      return 'centerRight';
+      return 'Alignment.centerRight';
     if (x == -1.0 && y == 1.0)
-      return 'bottomLeft';
+      return 'Alignment.bottomLeft';
     if (x == 0.0 && y == 1.0)
-      return 'bottomCenter';
+      return 'Alignment.bottomCenter';
     if (x == 1.0 && y == 1.0)
-      return 'bottomRight';
+      return 'Alignment.bottomRight';
     return 'Alignment(${x.toStringAsFixed(1)}, '
                      '${y.toStringAsFixed(1)})';
   }
diff --git a/packages/flutter/test/painting/alignment_test.dart b/packages/flutter/test/painting/alignment_test.dart
index 5dbf5db..e7020ec 100644
--- a/packages/flutter/test/painting/alignment_test.dart
+++ b/packages/flutter/test/painting/alignment_test.dart
@@ -212,10 +212,10 @@
 
   test('AlignmentGeometry toString', () {
     expect(const Alignment(1.0001, 2.0001).toString(), 'Alignment(1.0, 2.0)');
-    expect(const Alignment(0.0, 0.0).toString(), 'center');
-    expect(const Alignment(-1.0, 1.0).add(const AlignmentDirectional(1.0, 0.0)).toString(), 'bottomLeft + AlignmentDirectional.centerEnd');
+    expect(const Alignment(0.0, 0.0).toString(), 'Alignment.center');
+    expect(const Alignment(-1.0, 1.0).add(const AlignmentDirectional(1.0, 0.0)).toString(), 'Alignment.bottomLeft + AlignmentDirectional.centerEnd');
     expect(const Alignment(0.0001, 0.0001).toString(), 'Alignment(0.0, 0.0)');
-    expect(const Alignment(0.0, 0.0).toString(), 'center');
+    expect(const Alignment(0.0, 0.0).toString(), 'Alignment.center');
     expect(const AlignmentDirectional(0.0, 0.0).toString(), 'AlignmentDirectional.center');
     expect(const Alignment(1.0, 1.0).add(const AlignmentDirectional(1.0, 1.0)).toString(), 'Alignment(1.0, 2.0) + AlignmentDirectional.centerEnd');
   });
diff --git a/packages/flutter/test/painting/decoration_test.dart b/packages/flutter/test/painting/decoration_test.dart
index a7c647d..d66c332 100644
--- a/packages/flutter/test/painting/decoration_test.dart
+++ b/packages/flutter/test/painting/decoration_test.dart
@@ -352,8 +352,8 @@
       '   When DecorationImagePainter.paint() was called, there was no text\n'
       '   direction provided in the ImageConfiguration object to match.\n'
       '   The DecorationImage was:\n'
-      '     DecorationImage(SynchronousTestImageProvider(), center, match\n'
-      '     text direction, scale: 1.0)\n'
+      '     DecorationImage(SynchronousTestImageProvider(),\n'
+      '     Alignment.center, match text direction, scale: 1.0)\n'
       '   The ImageConfiguration was:\n'
       '     ImageConfiguration(size: Size(100.0, 100.0))\n'
     );
diff --git a/packages/flutter/test/painting/gradient_test.dart b/packages/flutter/test/painting/gradient_test.dart
index 4503825..fe946ab 100644
--- a/packages/flutter/test/painting/gradient_test.dart
+++ b/packages/flutter/test/painting/gradient_test.dart
@@ -187,7 +187,7 @@
         ],
       ).toString(),
       equals(
-        'LinearGradient(topLeft, bottomLeft, [Color(0x33333333), Color(0x66666666)], null, TileMode.clamp)',
+        'LinearGradient(Alignment.topLeft, Alignment.bottomLeft, [Color(0x33333333), Color(0x66666666)], null, TileMode.clamp)',
       ),
     );
   });
diff --git a/packages/flutter/test/rendering/box_test.dart b/packages/flutter/test/rendering/box_test.dart
index 3368cd0..b8e3e81 100644
--- a/packages/flutter/test/rendering/box_test.dart
+++ b/packages/flutter/test/rendering/box_test.dart
@@ -517,7 +517,7 @@
           '   parentData: MISSING\n'
           '   constraints: MISSING\n'
           '   size: MISSING\n'
-          '   alignment: center\n'
+          '   alignment: Alignment.center\n'
           '   textDirection: ltr\n'),
     );
   });
diff --git a/packages/flutter/test/rendering/image_test.dart b/packages/flutter/test/rendering/image_test.dart
index 55c1d91..b670e93 100644
--- a/packages/flutter/test/rendering/image_test.dart
+++ b/packages/flutter/test/rendering/image_test.dart
@@ -37,7 +37,7 @@
         '   constraints: BoxConstraints(25.0<=w<=100.0, 25.0<=h<=100.0)\n'
         '   size: Size(25.0, 25.0)\n'
         '   image: $squareImage\n'
-        '   alignment: center\n'
+        '   alignment: Alignment.center\n'
         '   invertColors: false\n'
         '   filterQuality: low\n'
       ),
diff --git a/packages/flutter/test/rendering/limited_box_test.dart b/packages/flutter/test/rendering/limited_box_test.dart
index 601d153..063e2c3 100644
--- a/packages/flutter/test/rendering/limited_box_test.dart
+++ b/packages/flutter/test/rendering/limited_box_test.dart
@@ -36,7 +36,7 @@
         ' │ parentData: <none>\n'
         ' │ constraints: BoxConstraints(w=800.0, h=600.0)\n'
         ' │ size: Size(800.0, 600.0)\n'
-        ' │ alignment: center\n'
+        ' │ alignment: Alignment.center\n'
         ' │ minWidth: 0.0\n'
         ' │ maxWidth: Infinity\n'
         ' │ minHeight: 0.0\n'
@@ -122,7 +122,7 @@
         ' │ parentData: <none>\n'
         ' │ constraints: BoxConstraints(w=800.0, h=600.0)\n'
         ' │ size: Size(800.0, 600.0)\n'
-        ' │ alignment: center\n'
+        ' │ alignment: Alignment.center\n'
         ' │ minWidth: 10.0\n'
         ' │ maxWidth: 500.0\n'
         ' │ minHeight: 0.0\n'
@@ -158,7 +158,7 @@
         ' │ parentData: <none>\n'
         ' │ constraints: BoxConstraints(w=800.0, h=600.0)\n'
         ' │ size: Size(800.0, 600.0)\n'
-        ' │ alignment: center\n'
+        ' │ alignment: Alignment.center\n'
         ' │ minWidth: 10.0\n'
         ' │ maxWidth: use parent maxWidth constraint\n'
         ' │ minHeight: use parent minHeight constraint\n'
@@ -173,5 +173,4 @@
       ),
     );
   });
-
 }
diff --git a/packages/flutter/test/widgets/basic_test.dart b/packages/flutter/test/widgets/basic_test.dart
index e8e4e7e..32d75ca 100644
--- a/packages/flutter/test/widgets/basic_test.dart
+++ b/packages/flutter/test/widgets/basic_test.dart
@@ -327,11 +327,11 @@
   test('UnconstrainedBox toString', () {
     expect(
       const UnconstrainedBox(constrainedAxis: Axis.vertical,).toString(),
-      equals('UnconstrainedBox(alignment: center, constrainedAxis: vertical)'),
+      equals('UnconstrainedBox(alignment: Alignment.center, constrainedAxis: vertical)'),
     );
     expect(
       const UnconstrainedBox(constrainedAxis: Axis.horizontal, textDirection: TextDirection.rtl, alignment: Alignment.topRight).toString(),
-      equals('UnconstrainedBox(alignment: topRight, constrainedAxis: horizontal, textDirection: rtl)'),
+      equals('UnconstrainedBox(alignment: Alignment.topRight, constrainedAxis: horizontal, textDirection: rtl)'),
     );
   });
 
diff --git a/packages/flutter/test/widgets/container_test.dart b/packages/flutter/test/widgets/container_test.dart
index d081473..f0b0da9 100644
--- a/packages/flutter/test/widgets/container_test.dart
+++ b/packages/flutter/test/widgets/container_test.dart
@@ -94,7 +94,7 @@
         '           │ parentData: offset=Offset(7.0, 7.0) (can use size)\n'
         '           │ constraints: BoxConstraints(w=39.0, h=64.0)\n'
         '           │ size: Size(39.0, 64.0)\n'
-        '           │ alignment: bottomRight\n'
+        '           │ alignment: Alignment.bottomRight\n'
         '           │ widthFactor: expand\n'
         '           │ heightFactor: expand\n'
         '           │\n'
@@ -167,7 +167,7 @@
         '           │ parentData: offset=Offset(7.0, 7.0) (can use size)\n'
         '           │ constraints: BoxConstraints(w=39.0, h=64.0)\n'
         '           │ size: Size(39.0, 64.0)\n'
-        '           │ alignment: bottomRight\n'
+        '           │ alignment: Alignment.bottomRight\n'
         '           │ widthFactor: expand\n'
         '           │ heightFactor: expand\n'
         '           │\n'
@@ -265,7 +265,7 @@
         '           │ layer: null\n'
         '           │ semantics node: null\n'
         '           │ size: Size(39.0, 64.0)\n'
-        '           │ alignment: bottomRight\n'
+        '           │ alignment: Alignment.bottomRight\n'
         '           │ textDirection: null\n'
         '           │ widthFactor: expand\n'
         '           │ heightFactor: expand\n'
@@ -392,7 +392,7 @@
         '           │ isBlockingSemanticsOfPreviouslyPaintedNodes: false\n'
         '           │ isSemanticBoundary: false\n'
         '           │ size: Size(39.0, 64.0)\n'
-        '           │ alignment: bottomRight\n'
+        '           │ alignment: Alignment.bottomRight\n'
         '           │ textDirection: null\n'
         '           │ widthFactor: expand\n'
         '           │ heightFactor: expand\n'
diff --git a/packages/flutter/test/widgets/overflow_box_test.dart b/packages/flutter/test/widgets/overflow_box_test.dart
index 20a8687..2dd5ef7 100644
--- a/packages/flutter/test/widgets/overflow_box_test.dart
+++ b/packages/flutter/test/widgets/overflow_box_test.dart
@@ -44,7 +44,7 @@
         .where((DiagnosticsNode n) => !n.isFiltered(DiagnosticLevel.info))
         .map((DiagnosticsNode n) => n.toString()).toList();
     expect(description, <String>[
-      'alignment: center',
+      'alignment: Alignment.center',
       'minWidth: 1.0',
       'maxWidth: 2.0',
       'minHeight: 3.0',