Add Configuration for vertical Despawn Ranges

[notTamion]

resolves #10177
config naming/structure might need some changes, i didn't wanna break existing configs so i just did it like this.

currently doesn't work for Raiders as those have extra checking logic in the removeWhenFarAway method, so i am not quite sure what to do about those

EDIT: also wanted to add that i am not sure if the normal despawn range should still impact the y axis. since your x axis is going to be higher then your y axis 99 % of the time anyways i will just have it keep affecting that aswell

[Machine-Maker]

I'm not sold on the format for the config with this change. There are several options that I can think of that I'd prefer

despawn-ranges:
    monster:
        hard:
            xz: 30 # or "horizontal"
            y: 5 # or "vertical"
        soft: 20 # just putting a numerical value would mean it applies to both (as it does now)

or

despawn-ranges:
    monster:
        hard: 30
        soft: 20
        soft-y: 5 # basically the `-y` value wouldn't even be in the config if it wasn't being used

[notTamion]

is there an existing way i can add optional configurations like that?

[lynxplay]

As you already said, this does not currently "work", as the distanceSqrt still takes into account the y diff.
Given we already have changes to basically every line in this section, I think it would be fair to just completely rewrite this logic
in a new paper block without consideration of keeping old code around/minimizing diff (given that this isn't minimal diff either, every line is touched beyond the two discard calls).

This would also heavily improve the variable names, making this whole mess a lot easier to read.

[notTamion]

alright i will probably be working on the custom serializer and the rewrite tomorrow

[notTamion]

Implemented the requested changes