clean up the TracingState API (#21514)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21514
ghimport-source-id: 6a9b6fdd7e696ea29e8715482708efe897230e4d
Reviewed By: jamesr66a
Differential Revision: D15719980
Pulled By: zdevito
fbshipit-source-id: 3de2746c3f3c3de4111b4cb73f4c4acedbf28862
