- Add the missing flutterEmbedding v2 meta-data to 8 manifests that still
used the removed v1 embedding
- Drop stale package attributes from covid19_mobile_app debug/profile
manifests that conflicted with its namespace
- Override gallery_saver_plus's hardcoded compileSdk 31 in image_editor so
its dependencies resolve (documented AAR metadata check now passes)
- Document that the three Firebase apps need a developer-provided
google-services.json before they can build
