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

tests/wpt/meta-legacy-layout/gamepad/not-fully-active.html.ini

@@ -1,3 +0,0 @@
-[not-fully-active.html]
-  [calling getGamepads() in a non-fully-active document]
-    expected: FAIL

tests/wpt/meta/gamepad/not-fully-active.html.ini

@@ -1,3 +0,0 @@
-[not-fully-active.html]
-  [calling getGamepads() in a non-fully-active document]
-    expected: FAIL