Summary:
Add resource monitor object to fbzmq library to monitor CPU and memory. User can use
the object to query RSS memory, cpu usage, and optionally call API to monitor memory periodicially
 and crash when reaches beyond a specified threshold limit.

Reviewed By: cenzhao

Differential Revision: D8873504

fbshipit-source-id: a445fdd580da82c55fba09c43f46f60bb9f1149a