KRaft controller does not handle simultaneous broker expirations correctly

In `ReplicationControlManager.fenceStaleBrokers`, we find all of the current stale replicas and attempt to remove them from the ISR. However, when multiple expirations occur at once, we do not properly accumulate the ISR changes. For example, I ran a test where the ISR of a partition was initialized to [1, 2, 3]. Then I triggered a timeout of replicas 2 and 3 at the same time. The records that were generated by `fenceStaleBrokers` were the following:

ApiMessageAndVersion(PartitionChangeRecord(partitionId=0, topicId=_seg8hBuSymBHUQ1sMKr2g, isr=[1, 3], leader=1, replicas=null, removingReplicas=null, addingReplicas=null) at version 0), ApiMessageAndVersion(FenceBrokerRecord(id=2, epoch=102) at version 0), 
ApiMessageAndVersion(PartitionChangeRecord(partitionId=0, topicId=_seg8hBuSymBHUQ1sMKr2g, isr=[1, 2], leader=1, replicas=null, removingReplicas=null, addingReplicas=null) at version 0), 
ApiMessageAndVersion(FenceBrokerRecord(id=3, epoch=103) at version 0)]

First the ISR is shrunk to [1, 3] as broker 2 is fenced. We also see the record to fence broker 2. Then the ISR is modified to [1, 2] as the fencing of broker 3 is handled. So we did not account for the fact that we had already fenced broker 2 in the request.

A simple solution for now is to change the logic to handle fencing only one broker at a time.