[WIP] Otap enum attrs

[lquerel]

Not ready for review at all!

Change Summary

Refactor the OTAP receiver and exporter internal telemetry to use bounded, enum-based attributes, following the approach introduced for OTLP metrics.

This change:

• Reuses common signal and outcome attribute sets.
• Introduces a shared receiver rejection error type.
• Aligns OTAP and OTLP acknowledgement and rejection dimensions.
• Partitions exporter metrics by signal and terminal outcome.
• Replaces global latency aggregation with bounded per-signal/outcome buckets.
• Renames OTAP metric sets to follow receiver.otap.* and exporter.otap.* conventions.
• Updates the component telemetry documentation.

What issue does this PR close?

• Closes Alignment of Metric naming conventions and instrumentation #3300

How are these changes tested?

• Added tests verifying metric isolation across signal, outcome, rejection scope, and error type.
• Added tests verifying enum attributes are preserved in terminal snapshots and exported exactly once.
• Added tests for per-signal/outcome exporter latency aggregation.
• Ran focused OTAP receiver and exporter integration tests.
• cargo xtask check

Are there any user-facing changes?

Yes. OTAP internal metric names and attribute sets have changed. Metrics now use bounded signal, outcome, and error.type dimensions and consistently follow the receiver.otap.* and exporter.otap.* naming conventions.

Changelog

• Added a .chloggen/*.yaml entry
• This PR is a chore (indicated in title)
• This is a documentation-only PR.

[opentelemetry-pr-dashboard]

Pull request dashboard status

Status last refreshed: 2026-07-22 19:57:54 UTC.

• Waiting on: Author
• Next step: Move out of draft to request review.

This automated status or its linked feedback items may be incorrect. If something looks wrong, please report it with the result you expected.

[codecov]

Codecov Report

❌ Patch coverage is 84.14767% with 146 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.70%. Comparing base (7502e7d) to head (b97dca1).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3534      +/-   ##
==========================================
- Coverage   86.71%   86.70%   -0.02%     
==========================================
  Files         789      790       +1     
  Lines      319633   320174     +541     
==========================================
+ Hits       277179   277610     +431     
- Misses      41930    42040     +110     
  Partials      524      524              

Components	Coverage Δ
otap-dataflow	87.73% <84.14%> (-0.02%)	⬇️
query_engine	89.57% <ø> (ø)
otel-arrow-go	52.45% <ø> (ø)
quiver	92.20% <ø> (ø)

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