[flutter_tools] migrate FlutterView to new vm_service (#55341)

Move FlutterView and related RPCs to the package:vm_service implementation. Update some getIsolate calls with catchError to match previous behavior.

- Updates tests that were previously mocking FlutterViews to use real views
- Moves the FlutterView cache from VM to FlutterDevice
- Catch SentinelException during Isolate.kill