Gh/taylorrobie/timer cleanup (#45361)
Summary:
This PR cleans up some of the rough edges around `Timer` and `Compare`
* Moves `Measurement` to be dataclass based
* Adds a bunch of type annotations. MyPy is now happy.
* Allows missing entries in `Compare`. This is one of the biggest usability issues with `Compare` right now, both from an API perspective and because the current failure mode is really unpleasant.
* Greatly expands the testing of `Compare`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45361
Test Plan: Changes to Timer are covered under existing tests, changes to `Compare` are covered by the expanded `test_compare` method.
Reviewed By: bwasti
Differential Revision: D23966816
Pulled By: robieta
fbshipit-source-id: 826969f73b42f72fa35f4de3c64d0988b61474cd
