Migrate game_template to Material 3

[miquelbeltran]

Migrated game_template to Material 3

Basically, the only thing that changes is the ElevatedButton that has been replaced by a FilledButton.

Before Material 3

With Material 3

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 updated/added relevant documentation (doc comments with ///).
• [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-devrel channel on Discord.

[miquelbeltran]

Looking at the failing test

[miquelbeltran]

The test failure is caused by the _SettingsLine for Reset Progress. I guess the Material 3 font is a bit larger, and it causes the menu to overflow for 4 pixels. Just changing the text to Reset Progres (one char less) the test passes. Trying to look for a solution now.