Gamepad: Align closer to spec and implement missing slots (#31385)

* Implement missing gamepad slots, align to spec more

- Fixes TODO's from initial gamepad implementation
- Adds some missing spec steps

* Only handle gamepad events when pref is enabled

* Return empty list in getGamepads if document not active

* ./mach fmt

* Update getGamepads to return an array instead of GamepadList

* Add spec link for [[exposed]] slot

* Remove failing test expectations for not-fully-active

* A few fixes

- Change should_notify to has_gesture
- Add spec links and TODO to navigator
- Remove unneeded clone from GamepadList::list
- Move gamepadconnected event firing into has_gesture block

* Use queue_with_canceller for tasks and add expects

* Explicitly check for gamepad user gesture

* Move user gesture check into separate function

* Change contains_user_gesture to be a gamepad function

* mach fmt

* Change axis/button threshold constants to be private to module

components/script/dom/gamepadlist.rs

@@ -48,6 +48,14 @@ impl GamepadList {
     pub fn remove_gamepad(&self, index: usize) {
         self.list.borrow_mut().remove(index);
     }
+
+    pub fn list(&self) -> Vec<Option<DomRoot<Gamepad>>> {
+        self.list
+            .borrow()
+            .iter()
+            .map(|gamepad| Some(DomRoot::from_ref(&**gamepad)))
+            .collect()
+    }
 }
 
 impl GamepadListMethods for GamepadList {