Re-land text wrapping/color PR (#22831)

This attempts to re-land #22656.

There are two changes from the original:

I turned off wrapping completely when not sending output to a terminal. Previously I had defaulted to wrapping at and arbitrary 100 chars in that case, just to keep long messages from being too long, but that turns out the be a bad idea because there are tests that are relying on the specific form of the output. It's also pretty arbitrary, and mostly people sending output to a non-terminal will want unwrapped text.

I found a better way to terminate ANSI color/bold sequences, so that they can be embedded within each other without needed quite as complex a dance with removing redundant sequences.

As part of these changes, I removed the Logger.supportsColor setter so that the one source of truth for color support is in AnsiTerminal.supportsColor.

*     Turn on line wrapping again in usage and status messages, adds ANSI color to doctor and analysis messages. (#22656)

    This turns on text wrapping for usage messages and status messages. When on a terminal, wraps to the width of the terminal. When writing to a non-terminal, wrap lines at a default column width (currently defined to be 100 chars). If --no-wrap is specified, then no wrapping occurs. If --wrap-column is specified, wraps to that column (if --wrap is on).

    Adds ANSI color to the doctor and analysis output on terminals. This is in this PR with the wrapping, since wrapping needs to know how to count visible characters in the presence of ANSI sequences. (This is just one more step towards re-implementing all of Curses for Flutter. :-)) Will not print ANSI sequences when sent to a non-terminal, or of --no-color is specified.

    Fixes ANSI color and bold sequences so that they can be combined (bold, colored text), and a small bug in indentation calculation for wrapping.

    Since wrapping is now turned on, also removed many redundant '\n's in the code.

packages/flutter_tools/lib/src/commands/create.dart

diff --git a/packages/flutter_tools/lib/src/commands/create.dart b/packages/flutter_tools/lib/src/commands/create.dart
index a99b75c..2711780 100644
--- a/packages/flutter_tools/lib/src/commands/create.dart
+++ b/packages/flutter_tools/lib/src/commands/create.dart
@@ -92,7 +92,7 @@
     argParser.addOption(
       'org',
       defaultsTo: 'com.example',
-      help: 'The organization responsible for your new Flutter project, in reverse domain name notation.\n'
+      help: 'The organization responsible for your new Flutter project, in reverse domain name notation. '
             'This string is used in Java package names and as prefix in the iOS bundle identifier.'
     );
     argParser.addOption(
@@ -174,7 +174,7 @@
     }
 
     if (Cache.flutterRoot == null)
-      throwToolExit('Neither the --flutter-root command line flag nor the FLUTTER_ROOT environment\n'
+      throwToolExit('Neither the --flutter-root command line flag nor the FLUTTER_ROOT environment '
         'variable was specified. Unable to find package:flutter.', exitCode: 2);
 
     await Cache.instance.updateAll();
@@ -230,7 +230,7 @@
         organization = existingOrganizations.first;
       } else if (1 < existingOrganizations.length) {
         throwToolExit(
-          'Ambiguous organization in existing files: $existingOrganizations.\n'
+          'Ambiguous organization in existing files: $existingOrganizations. '
           'The --org command line argument must be specified to recreate project.'
         );
       }
@@ -554,7 +554,7 @@
 /// if we should disallow the directory name.
 String _validateProjectDir(String dirPath, { String flutterRoot }) {
   if (fs.path.isWithin(flutterRoot, dirPath)) {
-    return 'Cannot create a project within the Flutter SDK.\n'
+    return 'Cannot create a project within the Flutter SDK. '
       "Target directory '$dirPath' is within the Flutter SDK at '$flutterRoot'.";
   }