Add compaction IT that verifies queues are cleared when tablets no longer need to compact.

[keith-turner]

This is follow on work for #3528 and #4394. Would be good to add an integration test for the changes in #4394. Unit test were added in #4394 that cover a narrow part of the code, but it would be good to verify things work end to end. Should be able to do something like the following in an IT.

• Create a table w/ N tablets
• Configure the table to use compaction group G1
• Start no compactors processes for G1. This should cause compactions to queue but not run.
• Add files and change compaction settings such that all tablets need to compact, could lower the compaction ratio and/or add more files per tablet than the compaction ratio
• Verify N tablets are queued for G1 via inspecting metrics
• Change the table config in such a way that no tablets need to compact, could raise the compaction ratio. Once the tablets no longer need to compact they should be cleared from the queue.
• Verify zero tablets are queued for G1 via inspecting metrics

[keith-turner]

It may be worthwhile to add this test to 2.1 and forward. The implementations are very different, but for this case hopefully the behavior is the same.

[DomGarguilo]

I can start looking into this.

[DomGarguilo]

Closed via #4466