Auto merge of #14839 - Permutatrix:iss-12939, r=emilio

Make offset parent queries less buggy.

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Offset parent queries, which are used in the getters for HTMLElement's `offsetParent`, `offsetTop`, `offsetLeft`, `offsetWidth`, and `offsetHeight`, are pretty busted. The most egregious bug is that, as reported in #12939, inline elements are treated as if they're not present in the document. This PR fixes that and all of the other bugs I could trace directly to the offset parent query code, but `offsetTop` and `offsetLeft` are still unreliable in certain circumstances for reasons I haven't looked into (#13708). Inline elements with no content are still treated as not present due to #13982, so #13944 isn't fixed with this PR, either.

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12939 and fix #12595

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- [X] There are tests for these changes

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tests/wpt/mozilla/meta/MANIFEST.json

@@ -6734,6 +6734,12 @@
             "url": "/_mozilla/css/meta_viewport_resize.html"
           }
         ],
+        "css/offset_properties_inline.html": [
+          {
+            "path": "css/offset_properties_inline.html",
+            "url": "/_mozilla/css/offset_properties_inline.html"
+          }
+        ],
         "css/test_variable_legal_values.html": [
           {
             "path": "css/test_variable_legal_values.html",