Package zookeeper setup scripts directly in pinot distribution

For new users of Pinot, it would be convenient to make the ZK setup scripts accessible directly from Pinot distribution. That will allows users to easily setup ZK cluster (in standalone or cluster mode), without directly pulling in the ZK distribution for setup. Apache Kafka project provides such a facility - [https://github.com/apache/kafka/blob/trunk/bin/zookeeper-server-start.sh](https://github.com/apache/kafka/blob/trunk/bin/zookeeper-server-start.sh)

Start by inspecting Pinot's distribution packaging and the linked Kafka zookeeper-server-start.sh example. Determine which Zookeeper setup scripts and standalone or cluster modes should be included, then verify that the packaged Pinot distribution supports setup without downloading the Zookeeper distribution separately.

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