nightly

Ensure BackupManager finishes during a Shut Down

- Added `BackupManager.Dispose` during the `Cleanup` phase. Ensuring it triggers during the exit progress bar.
- Added wait time (max 3 min) during `BackupManager.Dispose` before aborting the backup. Blocking `Cleanup` until it finishes or the time elapses.
- Added warning before closing if a backup is still in progress.
- Renamed `IsInBackupProcess` to `IsBackupActive`

Issue: I still see occasion where the backup thread doesn't wait and exits immediately. The `ProcessingQueue` jumps out to the finally directly even if a callback still hasn't finished.