Upgrade flutter version from 3.13.9 to 3.19.6

[FriesI23]

Upgrade flutter version to 3.19.6 (last stable version with dart 3.3 (3.3.4). Main reason for upgrading this version is:

• More stronger syntax checking (to prevent some bugs at async coding).
• To prevent falling too far behind Flutter's major version, which could be more difficult for future upgrades.
• Flutter project itself has fixed lot of bugs.

This update include following changes:

1. Fix unexpected warnings if enable use_build_context_synchronously, see here to get more information.

2. Breaking changes

   • Deprecate textScaleFactor in favor of TextScaler
   • Android Predictive Back
   • Deprecated imperative apply of Flutter's Gradle plugins

for full breaking changes with two versions, see Flutter 3.19 and Flutter 3.16.

3. Fix Scrollbar's Exception on desktop platforms (windows/macos/linux) in app's changelog and license dialog.

[FriesI23]

Review Done