Fill c.Request().Pattern field with route path to help standard library based middlewares

[aldas]

Fill c.Request().Pattern field with route path to help standard library based middlewares. For example Otel standard library Request/Response field extration uses Request.Pattern as route.

Relates to labstack/echo-contrib#141

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.02%. Comparing base (0954d6e) to head (d8c7f04).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2885   +/-   ##
=======================================
  Coverage   93.02%   93.02%           
=======================================
  Files          43       43           
  Lines        4456     4457    +1     
=======================================
+ Hits         4145     4146    +1     
  Misses        194      194           
  Partials      117      117           

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