Corner cases handling.

- crash on disappearing dataloaders,
- more robust binder callbacks processing,
- heavy unbind lifting moved to a separate thread to unblock Binder.

Bug: b/153874006
Test: atest PackageManagerShellCommandTest PackageManagerShellCommandIncrementalTest IncrementalServiceTest
Change-Id: Ie06c3c4dbecbdd552dd868e2092bf0ee48f8547a