Closes https://github.com/flutter/flutter/issues/152325.
This PR is large due to generate `flutter create --platforms android`. A quick summary:
- Moves the integration test from `packages/flutter_driver/test` to `dev/integration_tests`
- Created a sample Flutter app that draws a blue rectangle
- Forked a subset of `package:flutter_goldens` that will work on the standalone Dart VM
- Forked a subset of `goldens.dart` (from `flutter_test`) to `src/native/goldens.dart` (i.e. `matchesGoldenFile`)
This ... works locally, but as usual I have no idea if it will work on Skia Gold so let's roll some dice.
