feat(otelgin): add the WithGinMetricAttributes option to allow setting dynamic, per-request metric attributes based on *gin.Context

[tranngoclam]

• This PR adds a new func GinMetricAttributeFn of package otelgin.
• The main purpose is to extract the path template using FullPath() func of gin.Context

[dmathieu]

This is a breaking change. We should at least deprecate the method for one release before breaking user's apps.

[dmathieu]

In #5743, we added a new helper that took specifically a gin context.

[tranngoclam]

Hi @dmathieu , I have updated to use a new func instead

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.7%. Comparing base (cbc79e4) to head (4576990).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #6932   +/-   ##
=====================================
  Coverage   75.7%   75.7%           
=====================================
  Files        207     207           
  Lines      19396   19403    +7     
=====================================
+ Hits       14685   14692    +7     
  Misses      4275    4275           
  Partials     436     436           

Files with missing lines	Coverage Δ
...ntation/github.com/gin-gonic/gin/otelgin/config.go	100.0% <100.0%> (ø)
...umentation/github.com/gin-gonic/gin/otelgin/gin.go	92.6% <100.0%> (+0.1%)	⬆️

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