KAFKA-13370: add unit test for offset-commit metrics

[showuon]

Follow up for https://github.com/apache/kafka/pull/11413#issuecomment-970395759, to add tests for offset-commit metrics.

Committer Checklist (excluded from commit message)

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

[showuon]

@rhauch , per our discussion, here's the tests to be added. Thank you.

[showuon]

Failed tests are unrelated. Thank you.

    Build / JDK 17 and Scala 2.13 / kafka.admin.LeaderElectionCommandTest.[1] Type=Raft, Name=testTopicPartition, Security=PLAINTEXT
    Build / JDK 17 and Scala 2.13 / kafka.admin.LeaderElectionCommandTest.[1] Type=Raft, Name=testTopicPartition, Security=PLAINTEXT
    Build / JDK 8 and Scala 2.12 / kafka.admin.LeaderElectionCommandTest.[1] Type=Raft, Name=testAllTopicPartition, Security=PLAINTEXT
    Build / JDK 8 and Scala 2.12 / kafka.admin.LeaderElectionCommandTest.[1] Type=Raft, Name=testAllTopicPartition, Security=PLAINTEXT

[mimaison]

Thanks @showuon for the PR. It looks good, can you rebase it?