script/layout: Implement HTMLElement.scrollParent (#39110)

This new API allows getting the element which establishes an element's
scroll container. This will be used to properly implement
`scrollIntoView`. There is still work to do for this API and
`offsetParent` to properly handle ancestors which are
closed-shadow-hidden from the original query element.

In addition, fix an issue where inline boxes were establishing scrolling
containers (they shouldn't do that).

Testing: There are tests for this change.
Fixes: #39096.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

tests/wpt/meta/MANIFEST.json

@@ -232173,6 +232173,19 @@
        {}
       ]
      ],
+     "overflow-does-not-apply-to-inline-box.html": [
+      "f4c8a1816399ed368fb219bd1a4e49f61f18d083",
+      [
+       null,
+       [
+        [
+         "/css/reference/ref-filled-green-100px-square.xht",
+         "=="
+        ]
+       ],
+       {}
+      ]
+     ],
      "overflow-ellipsis-dynamic-001.html": [
       "2a9edba9308bf06009d7b9a27f21f1e0f1a231c7",
       [
@@ -630023,7 +630036,7 @@
       ]
      ],
      "scrollParent.html": [
-      "9faa0c9a3e92e38662ac77d25b08731fe00a7db3",
+      "344ee522ef2664e0b963e79812074f08f343f5bf",
       [
        null,
        {}