Collapse tracing_state.h into tracer.h (#21513)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21513
ghimport-source-id: 86278929818a8fc65684bd8f2ffac31460772fe9
Reviewed By: jamesr66a
Differential Revision: D15719982
Pulled By: zdevito
fbshipit-source-id: 56bb021dd949668562ea481c5ff0115a9ea2b02e
