[profiler] move _enable_dynamo_cache_lookup_profiler (#107720)
_enable_dynamo_cache_lookup_profiler used to get turned on when running `__enter__` or `__exit__` with the profiler. But it's possible to turn the profiler on and off without the context manager (e.g. with a schedule and calling `.step()`). Instead, we should put these calls (which are supposed to be executed when the profiler turns on/off) where `_enable_profiler()` and `_disable_profiler()` are called.
This puts `_enable_dynamo_cache_lookup_profiler` and `_set_is_profiler_enabled` into `_run_on_profiler_(start|stop)` and calls that on the 3 places where `_(enable|disable)_profiler` get called.
Differential Revision: [D48619818](https://our.internmc.facebook.com/intern/diff/D48619818)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107720
Approved by: https://github.com/wconstab
