#8015: Consolidate URL utils

[fregante]

What does this PR do?

• Complementary to https://github.com/pixiebrix/pixiebrix-extension/pull/8023

We have a couple of overlapping utilities and utilities appearing in unrelated files.

This also fixes a couple of bugs related to the baseURL removal

Checklist

• [x] Add tests and/or storybook stories
• [x] Designate a primary reviewer: @BLoe

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.45455% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 73.41%. Comparing base (1995795) to head (af6fa72). Report is 2 commits behind head on main.

:exclamation: Current head af6fa72 differs from pull request most recent head 9d9ebbf. Consider uploading reports for the commit 9d9ebbf to get more accurate results

Files	Patch %	Lines
src/integrations/UserDefinedIntegration.ts	75.00%	3 Missing :warning:
src/bricks/renderers/propertyTable.tsx	50.00%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8106      +/-   ##
==========================================
+ Coverage   73.37%   73.41%   +0.04%     
==========================================
  Files        1314     1312       -2     
  Lines       40722    40718       -4     
  Branches     7571     7561      -10     
==========================================
+ Hits        29879    29893      +14     
+ Misses      10843    10825      -18     

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