sys.settrace set some events without callbacks

[gaogaotiantian]

Bug report

Bug description:

sys.settrace sets PY_MONITORING_EVENT_BRANCH and PY_MONITORING_EVENT_EXCEPTION_HANDLED monitoring events but does not have any registered callbacks. Those two events should not generate any legacy trace events (and sys.settrace works fine without it for a long time), so we should just remove those.

This improves trace performance a bit (~3% for fib + empty tracefunc) as the events do not fire anymore.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-117385: Remove unhooked events on sys.settrace #117386