[SEMCONV] Metrics are incorrectly prefixed with metric.

[marcalff]

Fixes #3226

Changes

Please provide a brief description of the changes here.

• Fixed the semconv code generation for metrics, to emit the proper metric name

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.16%. Comparing base (bb68f49) to head (23c7a98).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3228   +/-   ##
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  Coverage   88.16%   88.16%           
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  Files         198      198           
  Lines        6224     6224           
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  Hits         5487     5487           
  Misses        737      737