fix: Make the builder name compatible with both flutter_gen and flutter_gen_runner (#592)

## What does this change?

Fixes #589 🎯

## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)
- [x] This change requires a documentation update

Author: b2nkuu

README.md

@@ -181,7 +181,7 @@ You can also configure generate options in the `build.yaml`, it will be read bef
 targets:
   $default:
     builders:
-      flutter_gen:
+      flutter_gen_runner: # or flutter_gen
         options: 
           output: lib/build_gen/ # Optional (default: lib/gen/)
           line_length: 120 # Optional (default: 80)

packages/command/test/flutter_gen_command_test.dart

@@ -14,7 +14,7 @@ void main() {
     );
     expect(
       await process.stdout.next,
-      equals('$flutterGenVersion Loading ... command${separator}pubspec.yaml'),
+      equals('$flutterGenVersion Loading ...'),
     );
     await process.shouldExit(0);
   });
@@ -26,7 +26,7 @@ void main() {
     );
     expect(
       await process.stdout.next,
-      equals('$flutterGenVersion Loading ... command${separator}pubspec.yaml'),
+      equals('$flutterGenVersion Loading ...'),
     );
     await process.shouldExit(0);
   });

packages/core/lib/settings/config.dart

@@ -37,10 +37,10 @@ Config loadPubspecConfig(File pubspecFile, {File? buildFile}) {
   if (buildFile != null && buildFile.existsSync()) {
     final buildContent = buildFile.readAsStringSync();
     final rawMap = loadYaml(buildContent) as Map?;
-    final optionBuildMap = rawMap?['targets']?[r'$default']?['builders']
-        ?['flutter_gen']?['options'];
-
-    if (optionBuildMap != null) {
+    final builders = rawMap?['targets']?[r'$default']?['builders'];
+    final optionBuildMap = (builders?['flutter_gen_runner'] ??
+        builders?['flutter_gen'])?['options'];
+    if (optionBuildMap is YamlMap) {
       final buildMap = {'flutter_gen': optionBuildMap};
       mergedMap = mergeMap([mergedMap, buildMap]);
       final buildLocaleHint = normalize(

packages/core/test/assets_gen_test.dart

@@ -225,6 +225,18 @@ void main() {
         await expectedAssetsGen(pubspec, generated, fact, build: build);
       },
     );
+
+    test(
+      'Assets on pubspec_assets.yaml and override with build_runner_assets.yaml ',
+      () async {
+        const pubspec = 'test_resources/pubspec_assets.yaml';
+        const build = 'test_resources/build_runnfer_assets.yaml';
+        const fact = 'test_resources/actual_data/build_assets.gen.dart';
+        const generated = 'test_resources/lib/build_gen/assets.gen.dart';
+
+        await expectedAssetsGen(pubspec, generated, fact, build: build);
+      },
+    );
   });
 
   group('Test generatePackageNameForConfig', () {

packages/core/test_resources/build_runner_assets.yaml

@@ -0,0 +1,9 @@
+name: test
+
+targets:
+  $default:
+    builders:
+      flutter_gen_runner:
+        options:
+          output: lib/build_gen/
+          line_length: 120