Migrate sampling_context to use SDK 3.0 attributes

[sentrivana]

See the Celery and WSGI sections in the migration guide

Closes getsentry/sentry-python#4505

[codecov]

❌ 3 Tests Failed:

Tests completed	Failed	Passed	Skipped
26581	3	26578	231

View the top 3 failed test(s) by shortest run time

tests.relay_integration.test_sdk::test_encoding[MONOLITH]

Stack Traces | 105s run time

#x1B[1m#x1B[31mtests/relay_integration/test_sdk.py#x1B[0m:98: in test_encoding
    assert event.data["project"] == settings.SENTRY_PROJECT
#x1B[1m#x1B[31mE   AttributeError: 'NoneType' object has no attribute 'data'#x1B[0m

tests.relay_integration.test_sdk::test_recursion_breaker[MONOLITH]

Stack Traces | 118s run time

#x1B[1m#x1B[31mtests/relay_integration/test_sdk.py#x1B[0m:81: in test_recursion_breaker
    with pytest.raises(Exception):
#x1B[1m#x1B[31mE   Failed: DID NOT RAISE <class 'Exception'>#x1B[0m

tests.relay_integration.test_sdk::test_simple[MONOLITH]

Stack Traces | 118s run time

#x1B[1m#x1B[31mtests/relay_integration/test_sdk.py#x1B[0m:64: in test_simple
    assert event
#x1B[1m#x1B[31mE   assert None#x1B[0m

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