Normalize URL paths: convert /.//p, /..//p, and //p to p

[theskim]

https://bugzilla.mozilla.org/show_bug.cgi?id=1874119

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #943 +/- ## ======================================= Coverage ? 81.82% ======================================= Files ? 21 Lines ? 3559 Branches ? 0 ======================================= Hits ? 2912 Misses ? 647 Partials ? 0 ```

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