Auto merge of #18542 - mhaessig:selector-tests, r=emilio

Land the test cases that should've landed with the selectors update

PR for #15448
- Added test for pseudo-element with whitespace #15335
- Added tests for empty values in `[att^=""]`, `[att$=""]` and `[att*=""]` selectors #15394 (tests for `[att~=""]` have been added with #15440)

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #15448
- [X] There are tests for these changes

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tests/wpt/metadata/MANIFEST.json

@@ -555945,7 +555945,7 @@
    "testharness"
   ],
   "dom/nodes/selectors.js": [
-   "019ceba60eaa07690fa3922995f53e65725d7f95",
+   "ec9fcd4f84ceca6f87efa5d12f328d6e552bfe33",
    "support"
   ],
   "dom/ranges/Range-attributes.html": [