Add metrics (counter + latency) for ZK reconnect attempts

**FEATURE REQUEST**

1. Please describe the feature you are requesting.

Metrics for ZK reconnects to be able monitor that and alert on frequent reconnect

2. Indicate the importance of this issue to you (blocker, must-have, should-have, nice-to-have).

MEDIUM (most of the reconnects handled by the Zk client itself)

there are log message for start/success/error on reconnect but monitoring on logs is not convenient.

4. Provide any additional detail on your proposed use case for this feature.

org.apache.bookkeeper.zookeeper.ZooKeeperClient (clientCreator) should track these metrics