feat(codegen): increment org contributors and assign seat in PR webhook handler

[srest2021]

fixes ENG-5942

depends on https://github.com/getsentry/sentry/pull/104371

Track an active contributor on a PR event webhook, if the repo has Seer and AI features enabled.

• Always increment the contributor's num actions.
• Only assign a seat to the contributor if it is not a bot or an external contributor.
• Assign a seat to a contributor on the second PR event (not the first).
• Seat assignment occurs in a task for robustness. We log a warning if it fails.

Extra notes

Info about the user's type (ie, bot or not) and association (ie, external contributor or not) can be obtained from the webhook payload, per the gh docs and gh enterprise docs.

• payload["pull_request"]["author_association"] is a required field for all pull_request, pull_request_review, and pull_request_review_comment action types, and also in gh enterprise. ✅ -> Added to all gh and gh enterprise fixtures.
• payload["pull_request"]["user"]["type"] is required for the pull_request.opened and pull_request.closed action types. ✅
• payload["pull_request"]["user"]["type"] is not required for pull_request.edited, or any pull_request_review or pull_request_review_comment action types. But I set up a gh app and triggered pull_request.edited and pull_request_review.submitted webhooks and the field was indeed present. It's also already present in the fixtures used in the tests. I'm assuming we can expect it for the majority of webhooks, unless the user somehow hasn't been "classified" already (?). If we can't find the user type we just assume the user isn't a bot (feedback welcome on this behavior).

[linear[bot]]

ENG-5942 Create Cron for Resetting ActiveContributors when Product Trial Ends

ENG-5935 Instrument Seer Event Requested Endpoint

[codecov[bot]]

:x: 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
29283	1	29282	234

View the top 1 failed test(s) by shortest run time

tests.sentry.integrations.github.test_utils.ShouldCreateOrIncrementContributorSeatTest::test_returns_false_when_seat_based_seer_disabled

Stack Traces | 2.5s run time

#x1B[1m#x1B[.../hostedtoolcache/Python/3.13.1........./x64/lib/python3.13/unittest/case.py#x1B[0m:58: in testPartExecutor
    yield
#x1B[1m#x1B[.../hostedtoolcache/Python/3.13.1........./x64/lib/python3.13/unittest/case.py#x1B[0m:651: in run
    self._callTestMethod(testMethod)
#x1B[1m#x1B[.../hostedtoolcache/Python/3.13.1........./x64/lib/python3.13/unittest/case.py#x1B[0m:606: in _callTestMethod
    if method() is not None:
#x1B[1m#x1B[31mE   TypeError: ShouldCreateOrIncrementContributorSeatTest.test_returns_false_when_seat_based_seer_disabled() missing 1 required positional argument: 'mock_quota'#x1B[0m

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