Updates all null safe dependencies to versions that allow 2.10 stable and 2.11 dev releases.
Also updates flutter_goldens and flutter_goldens_client to allow 2.11 dev.
Update all versions, specifically file which fixes some bugs that caused tests to fail if run in different orders:
- systemTemp directories created by MemoryFileSystem will allot names based on the file system instance instead of globally.
- MemoryFile.readAsLines()/readAsLinesSync() no longer treat a final newline in the file as the start of a new, empty line.
- RecordingFile.readAsLine()/readAsLinesSync() now always record a final newline.
