Migrate to pub workspaces (#4021)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **Chores**
- Updated all Dart SDK constraints to "^3.6.0", added a unified
workspace resolution key, and removed obsolete local dependency override
configurations.
- **CI/CD Improvements**
- Streamlined workflows and refined testing/coverage scripts by removing
outdated steps.
- **Tooling Enhancements**
- Introduced a new build generation script to automate build-runner
tasks.
- **Refactor**
- Applied minor code style refinements, including simplified constructor
syntax and streamlined control flow.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

examples/stackoverflow/pubspec.yaml

@@ -3,9 +3,11 @@ description: A new Flutter project.
 publish_to: "none"
 
 environment:
-  sdk: ">=3.0.0 <4.0.0"
+  sdk: ^3.6.0
   flutter: ">=1.17.0"
 
+resolution: workspace
+
 dependencies:
   dio: ^5.1.1
   flutter:

examples/stackoverflow/pubspec_overrides.yaml

@@ -1,16 +0,0 @@
-# melos_managed_dependency_overrides: flutter_riverpod,hooks_riverpod,riverpod,riverpod_lint,riverpod_analyzer_utils
-dependency_overrides:
-  flutter_riverpod:
-    path: ../../packages/flutter_riverpod
-  hooks_riverpod:
-    path: ../../packages/hooks_riverpod
-  riverpod:
-    path: ../../packages/riverpod
-  riverpod_analyzer_utils:
-    path: ../../packages/riverpod_analyzer_utils
-  riverpod_lint:
-    path: ../../packages/riverpod_lint
-  riverpod_annotation:
-    path: ../../packages/riverpod_annotation
-  riverpod_generator:
-    path: ../../packages/riverpod_generator