Support for request-level urlconf overrides

[NielkS]

Middlewares can override the default urlconf per request by setting a "urlconf" attribute to the inbound HttpRequest instance
(doc: https://docs.djangoproject.com/en/3.2/ref/request-response/#django.http.HttpRequest.urlconf )
This change adds support for this kind of override

[tim-schilling]

Thanks @NielkS for the PR! Can you add a test that verifies this functionality? Please also add a mention of this in the docs/changes.rst

[codecov]

Codecov Report

Merging #1488 (75dfe55) into main (15a581d) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 75dfe55 differs from pull request most recent head 9a232bc. Consider uploading reports for the commit 9a232bc to get more accurate results

@@           Coverage Diff           @@
##             main    #1488   +/-   ##
=======================================
  Coverage   86.58%   86.58%           
=======================================
  Files          35       35           
  Lines        1864     1864           
  Branches      262      262           
=======================================
  Hits         1614     1614           
  Misses        178      178           
  Partials       72       72           

Impacted Files	Coverage Δ
debug_toolbar/toolbar.py	92.04% <100.00%> (ø)

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[tim-schilling]

Ah, looks like the linter failed. You can run that locally with make style

[tim-schilling]

Rebased on main, added a test and updated changes documentation. Merging after CI passes.

[tim-schilling]

@NielkS thank you for the PR!