[DISCUSS] PIP-232: Introduce thread monitor to check if thread is blocked for long time.

[adobewjl]

Hello pulsar community,
I've opened `PIP-232: Introduce thread monitor to check if thread is blocked 
for long time.` to discuss.
For more details, please read the PIP at 
https://github.com/apache/pulsar/issues/18985
I'm looking forward to hearing what you think. 
Also the demo PR link at https://github.com/apache/pulsar/pull/18958