fix: URL encoding fixed while forwarding the request to the upstream in proxy mode

[dadrus]

Related issue(s)

closes #715

Checklist

• I agree to follow this project's Code of Conduct.
• I have read, and I am following this repository's Contributing Guidelines.
• I have read the Security Policy.
• I have referenced an issue describing the bug/feature request.
• I have added tests that prove the correctness of my implementation.

Description

Fixes the duplicate url encoding

[codecov]

Codecov Report

Merging #716 (6b8eddc) into main (353453f) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #716   +/-   ##
=======================================
  Coverage   89.49%   89.49%           
=======================================
  Files         213      213           
  Lines        9107     9107           
=======================================
  Hits         8150     8150           
  Misses        765      765           
  Partials      192      192           

Impacted Files	Coverage Δ
internal/fiber/middleware/xfmphu/request_url.go	100.00% <100.00%> (ø)
internal/handler/requestcontext/request_context.go	76.05% <100.00%> (-0.98%)	⬇️

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