feat(sdk): add otel.sdk.log.created self-observability metric

[cijothomas]

Changes

Adds the otel.sdk.log.created self-observability metric to the Logs SDK.
A u64 counter is bound once per SdkLogger (no attributes) and incremented
on every emit call that passes the telemetry-suppression check.

Merge requirement checklist

• CHANGELOG.md updated
• Unit tests added / N/A
  • Behavioral conformance will be covered by Weaver Live Check
    (in-progress: ci: add weaver live-check workflow for tower instrumentation (seed for #530) opentelemetry-rust-contrib#613).
    SDK control-flow paths (suppression early-return, post-shutdown
    no-op routing) are exercised by existing tests.
• Public API changes added to CHANGELOG.md / N/A
• Documentation updated / N/A

Notes

• Gated behind the experimental_metrics_bound_instruments Cargo feature,
  matching the existing otel.sdk.processor.log.processed metric. The
  semconv definition is still stability: development.
• Cross-SDK alignment: matches the Java/JS/Python pattern of incrementing
  after the per-emit gates and before processor dispatch. Rust's
  telemetry-suppression early-return is SDK-specific; no other reference
  SDK has an equivalent concept.
• Semconv: https://github.com/open-telemetry/semantic-conventions/blob/main/docs/otel/sdk-metrics.md#metric-otelsdklogcreated

[codecov]

Codecov Report

❌ Patch coverage is 29.54545% with 31 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.1%. Comparing base (0e78170) to head (8fb6833).

Files with missing lines	Patch %	Lines
opentelemetry-sdk/src/logs/logger.rs	29.5%	31 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3530     +/-   ##
=======================================
- Coverage   83.2%   83.1%   -0.1%     
=======================================
  Files        130     130             
  Lines      28246   28289     +43     
=======================================
+ Hits       23506   23517     +11     
- Misses      4740    4772     +32     

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[cijothomas]

Need to make some tweaks before merging.

[github-actions]

Thank you for your contribution! This PR has been automatically marked as stale because it has not had activity in the last 14 days. This may be due to a delay in review on our side or awaiting a response from you; either is fine, and we appreciate your patience.

It will be closed in 14 days if no further activity occurs. Pushing a new commit or leaving a comment will remove the stale label and keep the PR open.

[github-actions]

Closed as inactive. Thank you again for the contribution; please feel free to reopen this PR (or open a new one) if you'd like to continue the work.