Add platform_services sample (#8058)

* Add platform_services sample

* update build.gradle to use latest scripts

* use FlutterActivity

* Updated ExampleInstrumentedTest.java and deleted FlutterPlugin.groovy

* Remove getRandom code from main.dart

* remove unused import
diff --git a/examples/platform_services/pubspec.yaml b/examples/platform_services/pubspec.yaml
new file mode 100644
index 0000000..c0cbf0b
--- /dev/null
+++ b/examples/platform_services/pubspec.yaml
@@ -0,0 +1,9 @@
+name: platform_services
+
+dependencies:
+  flutter:
+    sdk: flutter
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter