Fix vector MBTiles resolution with flutter_map 8

[miakh]

Why

vector_map_tiles_mbtiles 1.2.1 says it supports vector_map_tiles 9, but a clean dependency solve still fails: the adapter pins mbtiles 0.4 / latlong2 0.9 while current vector_map_tiles 9 and flutter_map 8.3 use latlong2 0.10. This means the advertised upgrade path cannot currently be installed.

We found this while upgrading a production Flutter app that uses online raster maps and offline MBTiles vector maps.

What changes

• update the vector MBTiles adapter to mbtiles ^0.5.1 and latlong2 ^0.10.1
• bump the adapter to 1.2.2 and document the fix
• resolve the mixed-generation monorepo test workspace on the Flutter Map 8 dependency set
• re-enable the adapter tests in pull-request CI
• remove an import made redundant by mbtiles 0.5

Verification

• clean workspace dependency resolution on Flutter 3.47.2 / Dart 3.13.2
• dart analyze --fatal-infos --fatal-warnings vector_map_tiles_mbtiles
• flutter test --no-pub vector_map_tiles_mbtiles/test -r compact (3 tests)
• the same XYZ-to-TMS adapter behavior was verified in the consuming app, whose unsigned Android debug APK built successfully

Fixes #108

[miakh]

Closing this because the workspace-wide overrides force mbtiles 0.5 onto the sibling flutter_map_mbtiles package and break the repository's canonical CI. The repository-wide migration is already being handled in #121, so this partial migration would duplicate that work. Thanks.

[josxha]

Thanks anyways for the pr @miakh - and for the pr on vector_map_tiles