feat(otelmux): update http.route attribute to support request.Pattern

[flc1125]

see #6919

Although changes have been made, I'm somewhat unsure if this is what we need. 😅

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.

Project coverage is 80.9%. Comparing base (ac946ca) to head (c42b7a3).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...trumentation/github.com/gorilla/mux/otelmux/mux.go	66.6%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #7108   +/-   ##
=====================================
  Coverage   80.9%   80.9%           
=====================================
  Files        204     204           
  Lines      18064   18066    +2     
=====================================
+ Hits       14626   14628    +2     
  Misses      3011    3011           
  Partials     427     427           

Files with missing lines	Coverage Δ
...trumentation/github.com/gorilla/mux/otelmux/mux.go	95.6% <66.6%> (+<0.1%)	⬆️

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[akats7]

Unrelated to this PR, but based on that missing test coverage, it might be good to add a test case where GetPathTemplate returns an err, maybe using a path prefix or something

[flc1125]

Unrelated to this PR, but based on that missing test coverage, it might be good to add a test case where GetPathTemplate returns an err, maybe using a path prefix or something

I tried to cover this unit test, but because it's somewhat extreme, it's very difficult to trigger the execution that meets this part of the logic for coverage. So, I ignored it for now.

[flc1125]

Ready for merge.