Exclude codegen/lib/main.dart from static analysis (#52829)

dev/integration_tests/codegen/analysis_options.yaml

+# Take our settings from the repo's main analysis_options.yaml file, but add
+# an exclude for the lib/main.dart file, which requires a code-generated file,
+# in order to be properly analyzed.
+
+include: ../../../analysis_options.yaml
+
+analyzer:
+  exclude:
+    - lib/main.dart

dev/integration_tests/codegen/lib/main.dart

@@ -4,7 +4,7 @@
 
 import 'package:flutter/material.dart';
 import 'package:flutter_driver/driver_extension.dart';
-import 'message.dart' as generated; // ignore: uri_does_not_exist
+import 'message.dart' as generated;
 
 Future<void> main() async {
   enableFlutterDriverExtension();