Add prefix of remote events for RPC profiling (#40066)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40066
Builds on top of the previous PR to ensure that all remotely profiled events are prefixed with the key for the RPC that generated them.
The key is generated by the result of `_build_rpc_profiling_key` in `rpc/internal.py` and prefixed onto the event name. In order to do this, we set the current-key when creating the RPC in Python, retrieve the currently-set key in C++ and save a GloballyUniqueId -> key mapping to an in-memory map. When we receive an RPC with profiling information, we expect to receive this ID back, and look up the corresponding profiling key in the map.
The key is then added to all the remote events.
Tested by adding tests to ensure the key is added to all the remote events. Also added a UT which tests in under the multi-threading scenario, to ensure that the mapping's correctness is maintained when several RPCs are in the process of being created at once.
ghstack-source-id: 106316106
Test Plan: Unit test
Differential Revision: D22040035
fbshipit-source-id: 9215feb06084b294edbfa6e03385e13c1d730c43
