update mux default span name to include http method

[akats7]

Updates the default span name for the mux instrumentation to include the http method to align to the semconvs.

Added a test for default span naming and attributes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.7%. Comparing base (3ba7b7d) to head (a2ff5f2).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #7551   +/-   ##
=====================================
  Coverage   78.7%   78.7%           
=====================================
  Files        186     186           
  Lines      14694   14701    +7     
=====================================
+ Hits       11571   11581   +10     
+ Misses      2782    2780    -2     
+ Partials     341     340    -1     

Files with missing lines	Coverage Δ
...trumentation/github.com/gorilla/mux/otelmux/mux.go	97.9% <100.0%> (+2.2%)	⬆️

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[dmathieu]

This is nice.

[akats7]

@open-telemetry/go-approvers Can I please get another review

[flc1125]

Can you handle the conflict in the CHANGELOG

[MrAlias]

Looks like the slices import needs to be removed as it is no longer used:

Error: ./mux.go:9:2: "slices" imported and not used (typecheck)

[MrAlias]

Bumping the CI.