Update null safety warnings in prep for Dart 3 (#110998)

packages/flutter_tools/lib/src/base/logger.dart

@@ -722,6 +722,7 @@ class WindowsStdoutLogger extends StdoutLogger {
                .replaceAll('✓', '√')
                .replaceAll('🔨', '')
                .replaceAll('💪', '')
+               .replaceAll('⚠️', '!')
                .replaceAll('✏️', '');
     _stdio.stdoutWrite(windowsMessage);
   }

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

@@ -88,11 +88,11 @@ abstract class BuildSubCommand extends FlutterCommand {
       );
     } else {
       globals.printStatus(
-        'Building without sound null safety',
+        'Building without sound null safety ⚠️',
         emphasis: true,
       );
       globals.printStatus(
-        'For more information see https://dart.dev/null-safety/unsound-null-safety',
+        'Dart 3 will only support sound null safety, see https://dart.dev/null-safety',
       );
     }
     globals.printStatus('');

packages/flutter_tools/lib/src/isolated/resident_web_runner.dart

@@ -615,11 +615,11 @@ class ResidentWebRunner extends ResidentRunner {
         _logger!.printStatus('💪 Running with sound null safety 💪', emphasis: true);
       } else {
         _logger!.printStatus(
-          'Running with unsound null safety',
+          'Running without sound null safety ⚠️',
           emphasis: true,
         );
         _logger!.printStatus(
-          'For more information see https://dart.dev/null-safety/unsound-null-safety',
+          'Dart 3 will only support sound null safety, see https://dart.dev/null-safety',
         );
       }
     }

packages/flutter_tools/lib/src/run_hot.dart

@@ -1026,11 +1026,11 @@ class HotRunner extends ResidentRunner {
       globals.printStatus('💪 Running with sound null safety 💪', emphasis: true);
     } else {
       globals.printStatus(
-        'Running with unsound null safety',
+        'Running without sound null safety ⚠️',
         emphasis: true,
       );
       globals.printStatus(
-        'For more information see https://dart.dev/null-safety/unsound-null-safety',
+        'Dart 3 will only support sound null safety, see https://dart.dev/null-safety',
       );
     }
     globals.printStatus('');

packages/flutter_tools/test/general.shard/commands/build_test.dart

@@ -69,8 +69,8 @@ void main() {
     );
 
     FakeBuildSubCommand().test(unsound);
-    expect(
-        testLogger.statusText, contains('Building without sound null safety'));
+    expect(testLogger.statusText,
+        contains('Building without sound null safety ⚠️'));
 
     testLogger.clear();
     FakeBuildSubCommand().test(sound);