FlxMouseEventManager doesn't play nice with substates

[Gama11]

This is essentially the same issue as #1087 (which was resolved in #1934) but for FlxMouseEventManager.

A fix was proposed in #1961, but in my opinion it breaks too much code to be considered before a major version (5.0.0). Maybe there's a way of fixing this without breaking much code though?

[Geokureli]

this isn't a class I use very much, but I have some ideas after applying these changes to a local branch (this branch is outdated, so I made the changes manually).

With this proposed changes existing games will need to change all refs such as

FlxMouseEventManager.add(obj, onDown, null, onOver, onOut)
// becomes
FlxMouseEventManager.globalManager.add(obj, onDown, null, onOver, onOut)

While it works with surprsingly minimal changes to all HF libs, that's pretty verbose and cumbersome for devs. for cleaner code, what if we rename ObjectMouseData to FlxMouseEvent (or FlxTypedMouseEvent<T> and a typedef) and change the standard utilization to:

new FlxMouseEvent(obj, onDown, null, onOver, onOut)
// or
FlxMouseEvent.manage(obj, onDown, null, onOver, onOut)
// or
FlxMouseEvent.create(obj, onDown, null, onOver, onOut)
// or
FlxMouseEvent.track(obj, onDown, null, onOver, onOut)

We would also add a final manager arg, which defaults to the global manager. This is based on how FlxTween and FlxTimer work

Alternatively, we could recreate all the the old static functions of FlxMouseEventManager and create FlxMouseEvent.add and remove and the like, with the added manager arg

Option 3: we add FlxG.mouse.events or FlxG.mouseEvents and set it to the globalManager

[Geokureli]

I've made my proposed changes in #2540