Disabling the Instrument Name Validation under a new feature flag

[anujnegi270]

A fix for the feature [Feature]: A Dev Feature for Naming Convention used in Windows Performance Counters · Issue #2527 · open-telemetry/opentelemetry-rust and a related issue .

Fixes #
This fix is done under a feature flag experimental_metrics_disable_name_validation, where all types of instrument name are acceptable except empty names and names exceeding the length limit.

Changes

Defining the validation check function under the feature flag to bypass and return Ok().

Merge requirement checklist

• [✔️] CONTRIBUTING guidelines followed
• [✔️] Unit tests added/updated (if applicable)
• [✔️] Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: anujnegi270 (392a5ca, 8cf3ac0, 7212519, d051a06, 1099de4, c2f3da1, 02f9d56, 2eae4d0, 0602a08, 13d6ffd, 95ec73f, 830aed2, 655b815, 1149685, f8eeb7f, 44d5381, dfd1076, c4377ac)
• ✅ login: cijothomas / name: Cijo Thomas (7c9f561, 77d2535)
• ✅ login: lalitb / name: Lalit Kumar Bhasin (905b95a, 906e2b0)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.1%. Comparing base (fdc1151) to head (d051a06).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #2543     +/-   ##
=======================================
- Coverage   79.2%   79.1%   -0.1%     
=======================================
  Files        118     118             
  Lines      22511   22508      -3     
=======================================
- Hits       17829   17821      -8     
- Misses      4682    4687      +5     

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[cijothomas]

Merging to unblock users. This flag is expected to be removed in near future. I am working with OTel spec to relax the validation rules.