feat: Detect interpreter in shutdown state on thread spawn

[mitsuhiko]

This detects if the interpreter is already in shutdown state and no longer spawns a background thread.

Fixes#2299

[sl0thentr0py]

we have threads in all these places

➜ sentry-python git:(master) ag --depth=0 thread.start sentry_sdk
sentry_sdk/worker.py
70: self._thread.start()
sentry_sdk/sessions.py
123: thread.start()
sentry_sdk/profiler.py
921: self.thread.start()
sentry_sdk/monitor.py
56: thread.start()

[antonpirker]

@mitsuhiko I will take over and also add checks for the other places we start threads. Thanks for the contribution!

[antonpirker]

@sl0thentr0py I will merge this, because it fixes the one place where the problem arises that is mentioned in #2299

I will create another PR for the other places we start threads.

[antonpirker]

lgtm

The review has a valid point. This PR only fixes one place where threads are started. I will merge this PR and create another one for the other places where we start threads.

[antonpirker]

Oh, just saw Ivana already fixed this in our python312 branch.
Ok wurscht, I will make it work.