feat(segment-enrichment): Record seen segment names

[mjq]

Continues the work started in #103739.

As a first step to adding incremental segment name clustering to segment enrichment, record each seen segment name (like we do for transaction names in Sentry's event_manager). To work around the different signatures for transactions and segment spans, I extracted as much of the logic as I could into a second function, with one caller per scenario.

As with the previous PR, the changes are behind an org flag (organizations:normalize_segment_names_in_span_enrichment) for testing and easy rollback.

Closes ENG-5951.

[linear]

ENG-5951 Record incoming segment names to inform clustering

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
30044	1	30043	240

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

tests.sentry.core.endpoints.test_organization_index.OrganizationsCreateTest::test_valid_slugs

Stack Traces | 1.88s run time

#x1B[1m#x1B[.../core/endpoints/test_organization_index.py#x1B[0m:190: in test_valid_slugs
    response = self.get_success_response(name=input_slug, slug=input_slug)
#x1B[1m#x1B[.../sentry/testutils/cases.py#x1B[0m:628: in get_success_response
    assert_status_code(response, 200, 300)
#x1B[1m#x1B[.../sentry/testutils/asserts.py#x1B[0m:47: in assert_status_code
    assert minimum <= response.status_code < maximum, (
#x1B[1m#x1B[31mE   AssertionError: (500, b'{"detail":"Internal Error","errorId":null}')#x1B[0m
#x1B[1m#x1B[31mE   assert 500 < 300#x1B[0m
#x1B[1m#x1B[31mE    +  where 500 = <Response status_code=500, "application/json">.status_code#x1B[0m

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