Add new hot reload case string (#130008)

This change is for an internal IDE client to send a custom hot reload
request, as custom requests from the client must start with `$/`.

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packages/flutter_tools/lib/src/debug_adapters/flutter_adapter.dart

@@ -185,6 +185,8 @@ class FlutterDebugAdapter extends FlutterBaseDebugAdapter with VmServiceInfoFile
     switch (request.command) {
       case 'hotRestart':
       case 'hotReload':
+      // This convention is for the internal IDE client.
+      case r'$/hotReload':
         final bool isFullRestart = request.command == 'hotRestart';
         await _performRestart(isFullRestart, args?.args['reason'] as String?);
         sendResponse(null);

packages/flutter_tools/test/integration.shard/debug_adapter/flutter_adapter_test.dart

@@ -256,6 +256,24 @@ void main() {
           allowExtras: true,
       );
 
+      // Repeat the test for hot reload with custom syntax.
+      final Future<List<String>> customOutputEventsFuture = dap.client.stdoutOutput
+          // But skip any topLevelFunctions that come before the reload.
+          .skipWhile((String output) => output.startsWith('topLevelFunction'))
+          .take(2)
+          .toList();
+
+      await dap.client.customSyntaxHotReload();
+
+      expectLines(
+          (await customOutputEventsFuture).join(),
+          <Object>[
+            startsWith('Reloaded'),
+            'topLevelFunction',
+          ],
+          allowExtras: true,
+      );
+
       await dap.client.terminate();
     });
 

packages/flutter_tools/test/integration.shard/debug_adapter/test_client.dart

@@ -111,6 +111,11 @@ class DapTestClient {
     return custom('hotReload');
   }
 
+  /// Sends a custom request with custom syntax convention to the debug adapter to trigger a Hot Reload.
+  Future<Response> customSyntaxHotReload() {
+    return custom(r'$/hotReload');
+  }
+
   /// Sends a custom request to the debug adapter to trigger a Hot Restart.
   Future<Response> hotRestart() {
     return custom('hotRestart');