Support cancelling a region's compaction

[evenyag]

What type of enhancement is this?

Tech debt reduction

What does the enhancement do?

Now we don't provide a way to cancel background jobs especially the compaction job. Compaction may be a long-running task. When migrating a region or stopping a region, we may want to cancel the compaction.

Implementation challenges

Now we may only expose this feature to components inside the mito engine. We may pass a cancellation token to compaction and check it.