KAFKA-19987: Add metrics from KIP-1216 to ops.html

[lucasbru]

This commit adds the new thread-level rebalance listener callback metrics from KIP-1216 to the Streams Monitoring section in ops.html:

• tasks-revoked-latency-avg and tasks-revoked-latency-max
• tasks-assigned-latency-avg and tasks-assigned-latency-max
• tasks-lost-latency-avg and tasks-lost-latency-max

All metrics are at the INFO recording level and measure time in milliseconds.