Internally handle commit failures when rebalancing

[svroonland]

Committing when rebalancing will throw a RebalanceInProgressException. We should at the least include this in Offset.commitOrRetry or just completely handle it internally. If users want to customize commit behavior when rebalancing is going on for some reason, they can still observe the rebalancing diagnostic events.

Coming from #241

[Wosin]

Happy to at least take a crack at this.

[svroonland]

Much appreciated @Wosin!

However, I think I was too quick to create this issue though. This situation should not occur, since commits are not executed when rebalance is in progress. From Runloop lines 320:322.

      newPendingCommits <- if (!stillRebalancing && state.pendingCommits.nonEmpty)
                            doCommit(state.pendingCommits).as(Nil)
                          else ZIO.succeed(state.pendingCommits)

[svroonland]

Closing this, as explained above I'm pretty sure I falsely considered this to be an issue.