[libkineto] Refactor trace activities (#59360)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59360
Pull Request resolved: https://github.com/pytorch/kineto/pull/206
Replace ClientTraceActivity with GenericActivity.
In addition:
* Add a couple of new activity types for user annotations
* Simplify code for GPU-side user annotations
* Add accessor to containing trace span object in activities. Later we can replace this with a trace context / trace session object.
* Simplified MemoryTraceLogger
* Added early exit for cupti push/pop correlation ID
Reviewed By: ilia-cher
Differential Revision: D28231675
fbshipit-source-id: 7129f2493016efb4d3697094f24475e2c39e6e65
