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 (02f9d56, 392a5ca, 1149685, f8eeb7f, 2eae4d0, 13d6ffd, 1099de4, 830aed2, 0602a08, 44d5381)
• ✅ login: cijothomas / name: Cijo Thomas (7c9f561)
• ✅ login: lalitb / name: Lalit Kumar Bhasin (905b95a, 906e2b0)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.3%. Comparing base (144fdd9) to head (1099de4).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #2543     +/-   ##
=======================================
- Coverage   79.4%   79.3%   -0.2%     
=======================================
  Files        118     118             
  Lines      22526   22495     -31     
=======================================
- Hits       17898   17847     -51     
- Misses      4628    4648     +20     

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