Auto merge of #27255 - avr1254:master, r=jdm

Implemented HTMLFormElement.relList

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Updated the tests to reflect addition of rel and relList for HTMLFormElement, as well as porting those code snippets from HTMLAnchorElement.

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- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #27252  (GitHub issue number if applicable)

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because ___

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components/script/dom/webidls/HTMLFormElement.webidl

@@ -25,6 +25,9 @@ interface HTMLFormElement : HTMLElement {
            attribute boolean noValidate;
   [CEReactions]
            attribute DOMString target;
+  [CEReactions]
+           attribute DOMString rel;
+  [SameObject, PutForwards=value] readonly attribute DOMTokenList relList;
 
   [SameObject] readonly attribute HTMLFormControlsCollection elements;
   readonly attribute unsigned long length;