Add a URL that preserves the URL path when trying to resolve favicons.

[libklein]

Add an additional URL that appends /favicon.ico to the path of the URL. This works as follows:
https://google.com/my/path will become https://google.com/my/favicon.ico and https://google.com/my/path/ will become https://google.com/my/path/favicon.ico.

Fixes #8564.

Testing strategy

Added unit tests.

[libklein]

Im currently working on a PR that will fix various favicon download related issues by searching the page's HTML. This is just a quick fix that fixes this specific issue with the hope of making the backport.

[codecov-commenter]

Codecov Report

Base: 64.44% // Head: 64.37% // Decreases project coverage by -0.07% ⚠️

Coverage data is based on head (378d928) compared to base (56307e6).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 378d928 differs from pull request most recent head 08cffcf. Consider uploading reports for the commit 08cffcf to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8565      +/-   ##
===========================================
- Coverage    64.44%   64.37%   -0.07%     
===========================================
  Files          340      339       -1     
  Lines        44142    43996     -146     
===========================================
- Hits         28446    28319     -127     
+ Misses       15696    15677      -19     

Impacted Files	Coverage Δ
src/gui/IconDownloader.cpp	45.83% <100.00%> (+2.01%)	⬆️
...rc/fdosecrets/widgets/SettingsWidgetFdoSecrets.cpp	56.06% <0.00%> (-3.03%)	⬇️
src/fdosecrets/dbus/DBusMgr.cpp	52.20% <0.00%> (-1.47%)	⬇️
src/gui/DatabaseOpenWidget.cpp	56.65% <0.00%> (-0.62%)	⬇️
src/gui/Application.cpp	31.56% <0.00%> (-0.41%)	⬇️
src/cli/Import.cpp	87.18% <0.00%> (-0.32%)	⬇️
src/gui/DatabaseTabWidget.cpp	61.05% <0.00%> (-0.16%)	⬇️
src/cli/Command.cpp	87.78% <0.00%> (-0.13%)	⬇️
src/gui/DatabaseWidget.cpp	61.16% <0.00%> (-0.04%)	⬇️
src/core/Config.h	100.00% <0.00%> (ø)
... and 9 more

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[michaelk83]

Merge branch 'develop' into hotfix/8564-fix-favicon-download

@libklein FYI, the preferred approach based on their wiki to rebase, rather than merge:
https://github.com/keepassxreboot/keepassxc/wiki/Merge-strategy#merging-strategy-and-requirements

[phoerious]

Looks good to me. Might even be worth a backport, what do you think @droidmonkey?