Use semconv package for otelrestful

[dmathieu]

This switches otelrestful to use the semconv internal package, so it can migrate to stable HTTP semconv attributes.

Closes #6639

[codecov]

Codecov Report

Attention: Patch coverage is 87.78338% with 97 lines in your changes missing coverage. Please review.

Project coverage is 75.1%. Comparing base (d21dd87) to head (c711f43).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...o-restful/otelrestful/internal/semconv/httpconv.go	86.0%	42 Missing and 15 partials ⚠️
...go-restful/otelrestful/internal/semconv/v1.20.0.go	89.9%	11 Missing and 7 partials ⚠️
...lei/go-restful/otelrestful/internal/semconv/env.go	89.1%	15 Missing and 1 partial ⚠️
...ei/go-restful/otelrestful/internal/semconv/util.go	89.4%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6710     +/-   ##
=======================================
+ Coverage   74.5%   75.1%   +0.5%     
=======================================
  Files        199     203      +4     
  Lines      17529   18322    +793     
=======================================
+ Hits       13075   13771    +696     
- Misses      4070    4142     +72     
- Partials     384     409     +25     

Files with missing lines	Coverage Δ
...hub.com/emicklei/go-restful/otelrestful/restful.go	100.0% <100.0%> (ø)
...ei/go-restful/otelrestful/internal/semconv/util.go	89.4% <89.4%> (ø)
...lei/go-restful/otelrestful/internal/semconv/env.go	89.1% <89.1%> (ø)
...go-restful/otelrestful/internal/semconv/v1.20.0.go	89.9% <89.9%> (ø)
...o-restful/otelrestful/internal/semconv/httpconv.go	86.0% <86.0%> (ø)

... and 1 file with indirect coverage changes