refactor(otelgin): refactor HTTP server attributes to use new semconv package

[flc1125]

closed #6764

[flc1125]

This PR has some duplicated (conflicting) content with #6747, and I'm resolving the conflicts after one of them is merged.

[codecov]

Codecov Report

Attention: Patch coverage is 88.44221% with 92 lines in your changes missing coverage. Please review.

Project coverage is 75.5%. Comparing base (2c0f3ba) to head (efdde97).

Files with missing lines	Patch %	Lines
...gin-gonic/gin/otelgin/internal/semconv/httpconv.go	86.0%	42 Missing and 15 partials ⚠️
.../gin-gonic/gin/otelgin/internal/semconv/v1.20.0.go	89.9%	11 Missing and 7 partials ⚠️
....com/gin-gonic/gin/otelgin/internal/semconv/env.go	92.5%	9 Missing and 2 partials ⚠️
...com/gin-gonic/gin/otelgin/internal/semconv/util.go	89.4%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6778     +/-   ##
=======================================
+ Coverage   74.9%   75.5%   +0.5%     
=======================================
  Files        203     207      +4     
  Lines      18323   19116    +793     
=======================================
+ Hits       13738   14439    +701     
- Misses      4175    4241     +66     
- Partials     410     436     +26     

Files with missing lines	Coverage Δ
...ation/github.com/gin-gonic/gin/otelgin/gintrace.go	90.1% <100.0%> (+0.2%)	⬆️
...com/gin-gonic/gin/otelgin/internal/semconv/util.go	89.4% <89.4%> (ø)
....com/gin-gonic/gin/otelgin/internal/semconv/env.go	92.5% <92.5%> (ø)
.../gin-gonic/gin/otelgin/internal/semconv/v1.20.0.go	89.9% <89.9%> (ø)
...gin-gonic/gin/otelgin/internal/semconv/httpconv.go	86.0% <86.0%> (ø)