Compaction cannot be cancelled

As a result of the de-duplication cache based online compaction approach from OAK-3348 compaction cannot be cancelled any more (in the sense of OAK-3290).

As I assume we still need this feature we should look into ways to re-implement it on top of the current approach.

Also I figure implementing a partial compaction  approach on top of a commit scheduler (OAK-4122) would need a feature of this sort.