ref(integrations): Use ensure_integration_enabled decorator

[sentrivana]

Using the ensure_integration_enabled decorator which now supports not providing a function.

This is a best effort PR. We can't use the decorator everywhere.

• For instance, in the Mongo integration and couple more places, the integration class hasn't been defined yet at the point in time where we want to use the decorator. We can't move the definition up either because of interdependencies between things.
• Sometimes, applying the decorator makes the tests fail (this is the fix for one of those cases). Also e.g. in Starlite or one place in Starlette.

[sentrivana]

I'm aware of the failing Lint step but very confused by it:

sentry_sdk/integrations/flask.py:79: error: Untyped decorator makes function "sentry_patched_wsgi_app" untyped  [misc]

1. I didn't even touch this part of the code in this PR.
2. The decorator is properly typed...

[antonpirker]

Yeah!

Just some small nitpicking

[szokeasaurusrex]

Looks generally good to me, please check @antonpirker's comments before merging