Auto merge of #12383 - zeusintuivo:feature/11611, r=nox

Rename SharedKeyboardAndMouseEventInit to EventModifierInit

<!-- Please describe your changes on the following line: -->
- [X] renamed file SharedMouseAndKeyboardEventInit,
- [X] changed SharedKeyboardAndMouseEventInit to EventModifierInit.
- [X] Rebased mozilla/master into it.
- [x] Ran build and tidy test without errors

---
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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 #11611 (github issue number if applicable).

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tests/wpt/web-platform-tests/html/dom/interfaces.html

@@ -499,7 +499,7 @@ interface MouseEvent : UIEvent {
     boolean getModifierState (DOMString keyArg);
 };
 
-dictionary MouseEventInit : SharedKeyboardAndMouseEventInit {
+dictionary MouseEventInit : EventModifierInit {
     long           screenX = 0;
     long           screenY = 0;
     long           clientX = 0;
@@ -509,7 +509,7 @@ dictionary MouseEventInit : SharedKeyboardAndMouseEventInit {
     EventTarget?   relatedTarget = null;
 };
 
-dictionary SharedKeyboardAndMouseEventInit : UIEventInit {
+dictionary EventModifierInit : UIEventInit {
     boolean ctrlKey = false;
     boolean shiftKey = false;
     boolean altKey = false;