confighttp: make server span naming spec-compliant

[axw]

Description

Update the confighttp server span names to use the low-cardnality request pattern, rather than the full client-specified path, as described by the specification: https://opentelemetry.io/docs/specs/semconv/http/http-spans/#name.

Requires open-telemetry/opentelemetry-go-contrib#7192

Link to tracking issue

Fixes #12468

Testing

Added a unit test.

Documentation

None

[codeboten]

@axw this should be unblocked now that the deps update has been merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.60%. Comparing base (9b4911b) to head (3e1c30d).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #13088   +/-   ##
=======================================
  Coverage   91.59%   91.60%           
=======================================
  Files         505      506    +1     
  Lines       28479    28544   +65     
=======================================
+ Hits        26085    26147   +62     
- Misses       1880     1882    +2     
- Partials      514      515    +1     

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