[Tensorpipe Agent] Implement Global Interpreter Lock Wait Time Metric (#37851)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37851
Tracks `GilWaitTime` metric in the Tensorpipe RPC Agent.
ghstack-source-id: 103528374
Test Plan: CI
Differential Revision: D21339527
fbshipit-source-id: 7acc2cf304e1172de21b0e459f2c97430cd22834
