Dart 3.9 / Flutter 3.35 [first LLM release] (#2714)

I got carried away with Gemini and basically rewrote CI and the release
process for the new LLM reality. This work was largely completed by
Gemini.

- Bump all SDK versions to the current beta (3.9.0-0)
- Run `flutter channel beta`
- Wrote `ci_script.dart` to replace the bash scripts
- Converted repository to pub workspace #2499 
- Added llm.md and release.md
- Added redirect for deprecated Samples Index

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I have added sample code updates to the [changelog].
- [x] I updated/added relevant documentation (doc comments with `///`).

add_to_app/fullscreen/flutter_module_fullscreen/pubspec.yaml

@@ -1,10 +1,10 @@
-name: flutter_module
+name: flutter_module_fullscreen
 description: An example Flutter module.
-
 version: 1.0.0+1
+resolution: workspace
 
 environment:
-  sdk: ^3.7.0-0
+  sdk: ^3.9.0-0
 
 dependencies:
   flutter:

add_to_app/fullscreen/flutter_module_fullscreen/test/widget_test.dart

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:flutter/material.dart';
-import 'package:flutter_module/main.dart';
+import 'package:flutter_module_fullscreen/main.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:provider/provider.dart';
 

add_to_app/fullscreen/flutter_module_fullscreen/test_driver/example.dart

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:flutter_driver/driver_extension.dart';
-import 'package:flutter_module/main.dart' as app;
+import 'package:flutter_module_fullscreen/main.dart' as app;
 
 // This alternate entrypoint is used for espresso testing. See
 // https://pub.dev/packages/espresso for details.