KAFKA-13903: Queue size metric in QuorumController

[soarez]

In order to stay in-line with existing queue metrics in ControllerEventManager mbean, we need to include a queue size metric in KRaft mode.

The current size of the underlying queue in QuorumController needs to be exposed as:

kafka.controller:type=ControllerEventManager,name=EventQueueSize

Committer Checklist (excluded from commit message)

• [ ] Verify design and implementation
• [ ] Verify test coverage and CI build status
• [ ] Verify documentation (including upgrade notes)

➡ Link to JIRA

[soarez]

Hi Divij, thanks for having a look at this. The metric is documented. The goal is to bring it to KRaft.

[soarez]

@mumrah could you review this PR? Thanks

[soarez]

Thanks for the review @mumrah. I've applied your suggestion. It feels a bit strange to have the queue size supplier as an argument in QuorumControllerMetrics, but I like that the field is now final. Please have another look 🙏

[soarez]

@mumrah a couple of the builds succeeded but some failed with a flaky test — testFencedLeaderRecovery. There is already a JIRA for it https://issues.apache.org/jira/browse/KAFKA-14093

[soarez]

@mumrah could you take another look? Thanks

[soarez]

Rebased and simplified the changes. PTAL @mumrah