Implement stable http semantic conventions

[JamieDanielson]

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This is part of Semantic Convention Update: Tracking Issue #4572.

#4690 updated semantic conventions to 1.27, and includes both stable and experimental attributes.

This issue is for updating instrumentations to allow for dual emitting stable and experimental HTTP attributes.

• Add environment variable option OTEL_SEMCONV_STABILITY_OPT_IN that includes http and http/dup options as suggested in the Migration Plan.
• Instrumentations should default to current experimental HTTP attributes, with the option to emit only the stable HTTP attributes (with http as the env var value) or dual emit experimental and stable HTTP attributes (http/dup).

The next major version bump should drop this dual emit for HTTP attributes and default to only the stable HTTP attributes.

• [x] http client spans (#4940)
• [x] http server spans (#4978)
• [ ] grpc
• [ ] fetch
• [ ] xhr