KAFKA-14673; Add high watermark listener to Partition/Log layers

[dajac]

In the context of KIP-848, we implements are new group coordinator in Java. This new coordinator follows the architecture of the new quorum controller. It is basically a replicated state machine that writes to the log and commits its internal state when the writes are committed. At the moment, the only way to know when a write is committed is to use a delayed fetch. This is not ideal in our context because a delayed fetch can be completed before the write is actually committed to the log.

This patch proposes to introduce a high watermark listener to the Partition/Log layers. This will allow the new group coordinator to simply listen to changes and commit its state based on this. This mechanism is simpler and lighter as well.

Committer Checklist (excluded from commit message)

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

[hachikuji]

LGTM