Add BPF task stats tracepoint to TM and CPU thread pool executor
Add BPF task stats tracepoint to TM and CPU thread pool executor

Summary:
Allows attaching a BPF script to observe tasks behavior

Sample script, attaching those probes to a test binary (./buck-out/gen/common/services/cpp/test/thrift_2_async_server) is provided.

Reviewed By: yfeldblum

Differential Revision: D21526163

fbshipit-source-id: e976ddada1921c8c904d65aa9a558bbb45bf158f

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