Properly implement clearListeners and getListeners in order to allow changing order of listeners

The order in which the Controller Listeners are registered matters. It would be nice if there was a way to change this order without needing the application code to preserve its own copy of the listener list. That is being able to do

Array<ControllerListener> listenersCopy = new Array<>();
listenersCopy.addAll(Controllers.getListeners());
Controllers.clearListeners();
Controllers.addListener(priorityListener);
for(ControllerListener other : listenersCopy)
	Controllers.addListener(other);

Unfortunately this is currently impossible because JamepadControllerManager#getListeners() return an array containing only the CompositeControllerListener rather than returning the list of childs from CompositeControllerListener. Additionally, the internal listener ManageControllers should be excluded from this list exposed to the user.

What's needed

CompositeControllerListener.java

public LinkedList<ControllerListener> getListeners() {
    return listeners;
}

JamepadControllerManager.java

@Override
public Array<ControllerListener> getListeners() {
    Array<ControllerListener> array = new Array<>();
    LinkedList<ControllerListener> list = compositeListener.getListeners();
    boolean first = true;
    for(ControllerListener listener : list) {
        if(first) {
            first = false;
            continue;
        }
        array.add(listener);
    }
    return array;
}

No changes needed on clearListeners. If you guys agree with this idea, I'm willing to open a PR.

Further convenience

We could also add a function addPriorityListener to Controllers that would add the listener at the beginning of the list rather than the end, to allow users to do this even more easily.

Temporary workaround for people looking to do the same

ControllerManager manager = ReflectionUtil.callStatic(Controllers.class, "getManager");
Object compositeListener = ReflectionUtil.get(manager, "compositeListener");
LinkedList<ControllerListener> list = ReflectionUtil.get(compositeListener, "listeners");
list.add(1, this);

with ReflectionUtil available here.

Start with CompositeControllerListener.java and JamepadControllerManager.java, tracing getListeners and clearListeners through the public Controllers API. Verify that user-visible listeners preserve registration order while the internal ManageControllers listener is excluded, and confirm the proposed listener reordering workflow works with the existing project tests.