[Profiler] Move python tracing to unified event type (Part 2)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/78164
This PR finishes moving over the python tracer to use the unified event type. Things that changed:
1) The hacky after-the-fact splicing of python events in profiler_kineto.cpp is gone and python events now simply fold into the rest. (Yay!!!) This is a major BE win.
2) Added `ExtraFields<EventType::PyCall>` and `ExtraFields<EventType::PyCCall>`
3) The enter events (time + TraceKey) are now handled by RecordQueue for performance.
4) Python tracing now uses TSC for lower overhead.
Simplifications in profiler_python WRT part 1:
1) Rather than ValueCache emitting an intermediate value_t that gets further converted, load methods can now directly emit ExtraFields<...>
2) The complicated replay in profiler_python.cpp is replaced with a much simpler (and safer) pass to just pair start and end times.
3) During post processing we can now use `CallTypeHelper::map` to automatically pull in all events instead of having to loop over each the entries for each type manually. This will make it simpler to add new types of Python event later.
Differential Revision: [D36515869](https://our.internmc.facebook.com/intern/diff/D36515869/)
Approved by: https://github.com/aaronenyeshi
