Collapse tracing_state.h into tracer.h (#21563)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21563
ghimport-source-id: de87e5e621da33326a9d2cb8a57d82d355166479
Reviewed By: suo
Differential Revision: D15729499
Pulled By: zdevito
fbshipit-source-id: 17b3e2e71d004f08c4413e80091388ae9ac2df2b
