Throttle the ledger rollover for the broker

In Pulsar, the ledger rollover is split the data of a topic into multiple segments. For each ledger roll over operation, the metadata of the topic needs to be updated in the ZookKeeper. High ledger rollover frequency may lead to the ZookKeeper cluster in heavy workload. In order to make the ZookKeeper run more stable, we should limit the ledger rollover rate.