Merge changes from topic "snapshotctl_cleanup" into rvc-dev
* changes:
libsnapshot: SnapshotMergeStats::Start/Finish
libsnapshot: Expose SnapshotMergeStats
libsnapshot: delete WaitForMerge.
libsnapshot: handle errors in RemoveAllUpdateState appropriately.
libsnapshot: remove snapshots properly after flashing
libsnapshot: RemoveUpdateState on rollback.
libsnapshot: NeedSnapshotsInFirstStageMount don't test for IsRecovery
Allow ProcessUpdateState to be paused.
libsnapshot: Re-expose InitiateMerge and ProcessUpdateState
libsnapshot: Add prolog to RemoveAllUpdateStates.
snapshotctl don't auto-merge.
snapshotctl: init reports merge statistics
libsnapshot/test: Re-enable the failing tests