Add LaunchDarkly and OpenFeature integration

[cmanallen]

Adds LaunchDarkly and OpenFeature integration and extends the Scope with a flags property.

As flags are evaluated by an application they are stored within the Sentry SDK (lru cache). When an error occurs we fetch the flags stored in the SDK and serialize them on the event.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
14947	1	14946	4376

View the top 1 failed tests by shortest run time

tests.test_utils test_get_current_thread_meta_failed_to_get_main_thread

Stack Traces | 0.045s run time

tests/test_utils.py:916: in test_get_current_thread_meta_failed_to_get_main_thread
    thread.join()
.../hostedtoolcache/Python/3.6.15........./x64/lib/python3.6/threading.py:1052: in join
    if self is current_thread():
.../hostedtoolcache/Python/3.6.15........./x64/lib/python3.6/unittest/mock.py:939: in __call__
    return _mock_self._mock_call(*args, **kwargs)
.../hostedtoolcache/Python/3.6.15........./x64/lib/python3.6/unittest/mock.py:1001: in _mock_call
    result = next(effect)
E   StopIteration

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[sentrivana]

Will have a proper look soon -- just two comments regarding tox for now

[antonpirker]

Hey @cmanallen ! This is the best PR I have received ever! Great work.

The integrations should not change the Scope.

I have created an commit on your branch to illustrate how the flags could live on the integration rather than the scope (I hope you don't mind):
430387f

This way all the functionality is contained in the integration.
I also added some tests to show how you can now set the capacity of the buffer when initializing the Integration.

wdyt?

Feel free to make changes to my commit if you want to do things differently.

[cmanallen]

@antonpirker Reverted your commit per our conversation on Slack. Tl;dr the commit didn't work because we need to be tied to the scope to maintain flag isolation. After @sl0thentr0py's comment about it being fine to keep the flags on the scope if this change is permanent I think its appropriate to revert that change.