feat(attributes): remove gen AI reasoning effort

[constantinius]

Description

Removes gen_ai.request.reasoning_effort entirely and leaves gen_ai.request.reasoning.level as the only requested reasoning-effort convention.

The old key was not adopted, so this removes the deprecation/backfill metadata and the alias relationship added in #502 instead of carrying the old attribute through the normal deprecation pipeline.

Contributes to TET-2603.

PR Checklist

• I have run yarn test and verified that the tests pass.
• I have run yarn generate to generate and format code and docs.

If an attribute was added:

• The attribute is in a namespace (e.g. nextjs.function_id, not function_id)
• I have used the correct value for apply_scrubbing (i.e. manual or auto. Use never only for values that should never be scrubbed such as IDs)

If an attribute was deprecated:

• N/A — this removes the unused attribute instead of deprecating it.

Validation

• yarn generate
• yarn test

[linear-code]

TET-2603

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

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New Features ✨

Attributes

• Remove gen AI reasoning effort by constantinius in #503

• Deprecate gen AI reasoning effort by constantinius in #502
• Add sentry.pageload.span_id attribute by Lms24 in #495
• Add sentry.relay.ingress and sentry.relay.pipeline by loewenheim in #491
• Expand grpc attributes by lucas-zimerman in #460
• Add file.path and file.size by buenaflor in #458

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