feat(otelecho): add HTTP server metrics support for echo instrumentation

[Whitea029]

Description:

• Implement otelecho.WithServerMetrics() option to enable HTTP server metrics
• Add comprehensive test coverage for metrics functionality

Related Issue:

fix #7656

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.0%. Comparing base (6b59b27) to head (ee240d6).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #7668   +/-   ##
=====================================
  Coverage   78.9%   79.0%           
=====================================
  Files        186     186           
  Lines      14823   14871   +48     
=====================================
+ Hits       11703   11751   +48     
  Misses      2780    2780           
  Partials     340     340           

Files with missing lines	Coverage Δ
...tation/github.com/labstack/echo/otelecho/config.go	100.0% <100.0%> (ø)
...entation/github.com/labstack/echo/otelecho/echo.go	100.0% <100.0%> (ø)

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[flc1125]

Please fix the lint and also add a CHANGELOG.

[flc1125]

Please fix the lint and also add a CHANGELOG.

We can perform lint checks using make lint, and run unit tests with make test.