Gamepad: Remove GamepadList and fix dropped connection event on startup (#31684)

* Replace GamepadList

* Fix initial gamepad connection event from gilrs getting dropped

* Fix gamepad reconnection issues, use MutNullableDom

* Reduce some repetition in handle_gamepad_events

* Address feedback, move some steps to navigator methods

* Refactor internal navigator gamepad methods

* Add note re: unused gilrs index, adjust navigator gamepad methods

components/script/dom/gamepad.rs

@@ -199,6 +199,10 @@ impl Gamepad {
         }
     }
 
+    pub fn index(&self) -> i32 {
+        self.index.get()
+    }
+
     pub fn update_index(&self, index: i32) {
         self.index.set(index);
     }