fix(otelgin): consider OTEL_SEMCONV_STABILITY_OPT_IN for trace attributes

[flc1125]

fixed #7212

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.9%. Comparing base (5e0f783) to head (39af1fd).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #7215     +/-   ##
=======================================
- Coverage   80.9%   80.9%   -0.1%     
=======================================
  Files        204     204             
  Lines      18066   18065      -1     
=======================================
- Hits       14628   14627      -1     
  Misses      3011    3011             
  Partials     427     427             

Files with missing lines	Coverage Δ
...umentation/github.com/gin-gonic/gin/otelgin/gin.go	92.9% <100.0%> (-0.1%)	⬇️

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