Transaction name clustering: apply rules to `span.segment_name`

[jjbayer]

Open questions:

• [ ] What field do rules apply to?
• [x] Is this a dependency for dynamic sampling? Even if we only do trace-based sampling, should the transaction name in the trace be normalized? Answer: We need to call parametrize_dsc_transaction for standalone spans, either directly or by https://github.com/getsentry/relay/issues/3337).