[go_router_builder] Fix unnecessary whitespace in generated RelativeGoRouteData (#9875)

As can be seen in the [go_router_builder relative route example](https://github.com/flutter/packages/blob/main/packages/go_router_builder/example/lib/go_relative.g.dart), there is unnecessary whitespace in the generated output of `RelativeGoRouteData`.

This PR fixes the whitespace issue and adjusts `run_tests.dart` to catch similar issues/regressions in the future.

Closes flutter/flutter#174339.

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Author: LukasMirbt

packages/go_router_builder/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 4.0.1
+
+- Fixes unnecessary whitespace in generated `RelativeGoRouteData`. 
+
 ## 4.0.0
 
 - Make Route mixins public.

packages/go_router_builder/README.md

@@ -13,7 +13,7 @@ dependencies:
 dev_dependencies:
   # ...along with your other dev-dependencies
   build_runner: ^2.6.0
-  go_router_builder: ^3.3.0
+  go_router_builder: ^4.0.1
 ```
 
 ### Source code

packages/go_router_builder/example/lib/go_relative.g.dart

@@ -572,11 +572,10 @@ mixin $_mixinName on $routeDataClassName {
   }
 
   @override
-  String get routeConstructorParameters => '''
-    path: ${escapeDartString(path)},
-    ${caseSensitive ? '' : 'caseSensitive: $caseSensitive,'}
-    ${parentNavigatorKey == null ? '' : 'parentNavigatorKey: $parentNavigatorKey,'}
-''';
+  String get routeConstructorParameters =>
+      'path: ${escapeDartString(path)},'
+      '${caseSensitive ? '' : 'caseSensitive: $caseSensitive,'}'
+      '${parentNavigatorKey == null ? '' : 'parentNavigatorKey: $parentNavigatorKey,'}';
 
   @override
   String get routeDataClassName => 'RelativeGoRouteData';

packages/go_router_builder/example/lib/readme_excerpts.g.dart

@@ -2,7 +2,7 @@ name: go_router_builder
 description: >-
   A builder that supports generated strongly-typed route helpers for
   package:go_router
-version: 4.0.0
+version: 4.0.1
 repository: https://github.com/flutter/packages/tree/main/packages/go_router_builder
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+go_router_builder%22
 

packages/go_router_builder/lib/src/route_config.dart

@@ -61,12 +61,8 @@ Future<void> main() async {
       }
 
       // Apply consistent formatting to both generated and expected code for comparison.
-      final String generated = formatter.format(
-        results.join().replaceAll('\n', ''),
-      );
-      final String expected = formatter.format(
-        expectResult.replaceAll('\n', ''),
-      );
+      final String generated = formatter.format(results.join('\n\n').trim());
+      final String expected = formatter.format(expectResult.trim());
       expect(generated, equals(expected));
     }, timeout: const Timeout(Duration(seconds: 100)));
   }