feat(tracing): ignore configured HTTP status codes

[shahidul5]

Summary

• add tracing.ignored_http_status_codes, defaulting to [404]
• drop only matching main-request transactions after the response is available
• cover YAML, PHP, XML config and response behavior

Closes #958

Testing

• Not run locally: PHP and Composer are unavailable in this environment.
• git diff --check

Notes

• This is a breaking default; release notes and the external configuration migration documentation should explain how to retain 404 transaction tracing by setting tracing.ignored_http_status_codes: [].

AI assistance

I used AI assistance to research, implement, and review this change; I verified the code structure and diff manually.