Auto merge of #15799 - asajeffrey:script-window-xorigin-parent, r=nox

Implement dissimilar-origin window.parent and window.top

<!-- Please describe your changes on the following line: -->

This PR implements `window.parent` and `window.top` for dissimilar-origin windows.

This PR builds on #15536, only the last commit is part of this PR.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #14996 and fix #11660.
- [X] These changes do not require tests because there's already a parentage test in `mozilla/cross-origin-objects/cross-origin-objects.html`.

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tests/wpt/metadata/html/browsers/browsing-the-web/navigating-across-documents/navigation_unload_data_url.html.ini

@@ -1,6 +0,0 @@
-[navigation_unload_data_url.html]
-  type: testharness
-  expected: TIMEOUT
-  [Same-origin navigation started from unload handler]
-    expected: TIMEOUT
-

tests/wpt/metadata/html/browsers/origin/origin-of-data-document.html.ini

@@ -1,6 +1,5 @@
 [origin-of-data-document.html]
   type: testharness
-  expected: TIMEOUT
   [The origin of a 'data:' document in a frame is opaque.]
-    expected: TIMEOUT
+    expected: FAIL
 

tests/wpt/mozilla/meta/mozilla/cross-origin-objects/cross-origin-objects.html.ini

@@ -1,5 +0,0 @@
-[cross-origin-objects.html]
-  type: testharness
-  [Parentage of cross-origin windows]
-    expected: FAIL
-