Auto merge of #26450 - PeterZhizhin:add_referrerpolicy_to_list_of_relevant_mutations, r=jdm

Add referrerpolicy to list of relevant mutations

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

`img.referrerPolicy` change now mutates the image.
Not all `referrerPolicy` attribute changes result in an image update event.
Only valid changes are reflected.

All referrerpolicy tests inside `relevant-mutations.html` WPT test now pass.

---
<!-- 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 #26388

<!-- Either: -->
- [x] These have tests:
```
./mach test-wpt tests/wpt/web-platform-tests/html/semantics/embedded-content/the-img-element/relevant-mutations.html
```

components/script/dom/webidls/HTMLImageElement.webidl

@@ -27,6 +27,8 @@ interface HTMLImageElement : HTMLElement {
   readonly attribute unsigned long naturalHeight;
   readonly attribute boolean complete;
   readonly attribute USVString currentSrc;
+  [CEReactions]
+           attribute DOMString referrerPolicy;
   // also has obsolete members
 };