Add support for hot restart tests in DWDS with the frontend server

- Aligns the bootstrap script with Flutter tools for the DDC library
bundle format. This includes adding the dartReloadModifiedModules
callback and the script to wait until all sources are loaded before
calling main.
- Aligns the recompile code with Flutter tools. This includes adding
support for detecting invalidated files, using recompile-restart,
and writing a script that DWDS can use to detect files for a hot
restart.
- Refactors hot restart tests into shared test code that is now
tested both with the build daemon and the frontend server. Tests
that rely on build events are skipped in the frontend server by
design and tests that rely on deferring main are skipped with the
new DDC library bundle format until dart-lang/sdk#60528
is resolved. Tests are also renamed to use "restart" instead of
"reload" to distinguish from hot reload tests, which will be added
in a future CL.

Author: srujzs

dwds/test/build_daemon_hot_restart_correctness_test.dart

@@ -0,0 +1,37 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+@TestOn('vm')
+@Tags(['daily'])
+@Timeout(Duration(minutes: 2))
+library;
+
+import 'package:dwds/expression_compiler.dart';
+import 'package:test/test.dart';
+import 'package:test_common/test_sdk_configuration.dart';
+
+import 'common/hot_restart_correctness_common.dart';
+import 'fixtures/context.dart';
+
+void main() {
+  // Enable verbose logging for debugging.
+  final debug = false;
+  final canaryFeatures = false;
+  final moduleFormat = ModuleFormat.amd;
+  final compilationMode = CompilationMode.buildDaemon;
+
+  final provider = TestSdkConfigurationProvider(
+    verbose: debug,
+    canaryFeatures: canaryFeatures,
+    ddcModuleFormat: moduleFormat,
+  );
+
+  runTests(
+    provider: provider,
+    moduleFormat: moduleFormat,
+    compilationMode: compilationMode,
+    canaryFeatures: canaryFeatures,
+    debug: debug,
+  );
+}

dwds/test/build_daemon_hot_restart_test.dart

@@ -0,0 +1,37 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+@TestOn('vm')
+@Tags(['daily'])
+@Timeout(Duration(minutes: 2))
+library;
+
+import 'package:dwds/expression_compiler.dart';
+import 'package:test/test.dart';
+import 'package:test_common/test_sdk_configuration.dart';
+
+import 'common/hot_restart_common.dart';
+import 'fixtures/context.dart';
+
+void main() {
+  // Enable verbose logging for debugging.
+  final debug = false;
+  final canaryFeatures = false;
+  final moduleFormat = ModuleFormat.amd;
+  final compilationMode = CompilationMode.buildDaemon;
+
+  final provider = TestSdkConfigurationProvider(
+    verbose: debug,
+    canaryFeatures: canaryFeatures,
+    ddcModuleFormat: moduleFormat,
+  );
+
+  runTests(
+    provider: provider,
+    moduleFormat: moduleFormat,
+    compilationMode: compilationMode,
+    canaryFeatures: canaryFeatures,
+    debug: debug,
+  );
+}