Upgrade semconv to 1.32.0 for HTTP packages

[MrAlias]

• Remove TestHTTPServerDoesNotPanic/emtpy and TestHTTPClientDoesNotPanic/empty. We control all uses of this type.
• Updates otelrestful, otelgin, otelmux, otelhttptrace, and otelhttp.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.2%. Comparing base (99703a7) to head (9b90be2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #7383     +/-   ##
=======================================
- Coverage   82.4%   82.2%   -0.2%     
=======================================
  Files        205     205             
  Lines      18084   17949    -135     
=======================================
- Hits       14903   14762    -141     
- Misses      2743    2749      +6     
  Partials     438     438             

Files with missing lines	Coverage Δ
...lei/go-restful/otelrestful/internal/semconv/env.go	95.5% <100.0%> (+0.5%)	⬆️
...o-restful/otelrestful/internal/semconv/httpconv.go	87.5% <ø> (-1.5%)	⬇️
...ei/go-restful/otelrestful/internal/semconv/util.go	82.8% <ø> (ø)
....com/gin-gonic/gin/otelgin/internal/semconv/env.go	95.5% <100.0%> (+0.5%)	⬆️
...gin-gonic/gin/otelgin/internal/semconv/httpconv.go	89.1% <ø> (-1.3%)	⬇️
...com/gin-gonic/gin/otelgin/internal/semconv/util.go	82.8% <ø> (ø)
...ub.com/gorilla/mux/otelmux/internal/semconv/env.go	93.8% <100.0%> (+0.8%)	⬆️
...m/gorilla/mux/otelmux/internal/semconv/httpconv.go	87.5% <ø> (-1.5%)	⬇️
...b.com/gorilla/mux/otelmux/internal/semconv/util.go	82.8% <ø> (ø)
...tp/httptrace/otelhttptrace/internal/semconv/env.go	91.6% <100.0%> (+1.1%)	⬆️
... and 5 more

... and 1 file with indirect coverage changes

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