Auto merge of #25310 - pshaughn:attr_node, r=Manishearth

Attr is a Node, with consequences for many Node methods

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Attr is now a Node, as current WHATWG specs require. I think I did some unidiomatic things to make compareDocumentPosition work and it could use a look by someone more familiar with how to write concise Rust code. I also think the new cases in compareDocumentPosition lack tests; it is possible to compare the position of two attributes, or of an attribute and an element, and I don't think any tests are exercising that functionality.

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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 #25124

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- [ ] There are tests for these changes (existing cases of Node methods are well-tested, and there is a WPT test specifically for whether Attr is Node, but I'm not sure about new Node method cases)

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components/script/dom/webidls/Attr.webidl

@@ -8,7 +8,7 @@
  */
 
 [Exposed=Window]
-interface Attr {
+interface Attr : Node {
   [Constant]
   readonly attribute DOMString? namespaceURI;
   [Constant]
@@ -17,14 +17,8 @@ interface Attr {
   readonly attribute DOMString localName;
   [Constant]
   readonly attribute DOMString name;
-  [Constant]
-  readonly attribute DOMString nodeName; // historical alias of .name
   [CEReactions, Pure]
            attribute DOMString value;
-  [CEReactions, Pure]
-           attribute DOMString textContent; // historical alias of .value
-  [CEReactions, Pure]
-           attribute DOMString nodeValue; // historical alias of .value
 
   [Pure]
   readonly attribute Element? ownerElement;