AGP 9 Support

[ihadabs]

[gdelataillade]

Not planning to add support for AGP 9 right now, but in a few months. Feel free to open a PR though.

Docs: https://docs.flutter.dev/release/breaking-changes/migrate-to-agp-9

[Adityapanther]

@gdelataillade could you please check this pull #406 ?