VGDP snapshot leak when uploader fails to back up partial files

[Lyndon-Li]

As the configured behavior of uploader (kopia/restic), if some individual files fail to be backed up, the repo snapshot can still be created and the fails are reported as errors which are passed to the backup controllers.

When backup controllers see the errors, it marks the PVBs/DUs as failed. And the repo snapshot IDs are not recorded, as a result, the repo snapshots are not deleted during backup deletion.

[qiuming-best]

After our discussion, we reached one agreement:

Once the uploader failed to backup one specific file, we failed the backup immediately (Kopia has one option to fail fast)