chore: Updates HTTP attributes

[andyfleming]

Based on https://opentelemetry.io/docs/specs/semconv/http/http-spans/#http-server-semantic-conventions and https://github.com/open-telemetry/semantic-conventions/blob/main/model/trace/http.yaml

(Tests still need updated)

[dmathieu]

Note that the 1.21.0 semantic conventions recommend the use of an environment variable to make this transition smoother.
https://github.com/open-telemetry/semantic-conventions/blob/v1.21.0/docs/http/README.md

Not all SDKs are following this recommendation (it's a SHOULD, not a MUST). But IMHO, there should be an explicit decision on whether ruby should follow the recommendation or not.

[andyfleming]

@dmathieu Hadn't seen that. Thanks! I will take a look at what's involved in supporting OTEL_SEMCONV_STABILITY_OPT_IN here.

[github-actions]

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[kaylareopelle]

Hi @andyfleming! Are you still working on this? Would you like me to put a keep label on this PR?

[github-actions]

👋 This pull request has been marked as stale because it has been open with no activity. You can: comment on the issue or remove the stale label to hold stale off for a while, add the keep label to hold stale off permanently, or do nothing. If you do nothing this pull request will be closed eventually by the stale bot