Setters for Event Locations in Teleport Events

[NotSoDelayed]

Problem

Skript does not have a way to manipulate event locations for teleport related events.

Solution

This PR adds support for modifying said event values.

Additionally, I have unified PlayerPortalEvent and EntityPortalEvent into a single event class which also allows for a unified Skript documentation, as the core event logic of these events are exactly the same.

Testing Completed

My main objective prior to discovering the absence of these changers is to intercept portal usage to divert entities to another location. Specifically, I have a separate world that is for SMP, while also using the default nether world (world_nether). When you are returning from the nether, Minecraft will always send you to the main world instead of the origin world of the player previously came from.

The following code was used for testing:

on portal:
	teleport cause is nether portal
	player's world = world("world_nether")
	set {_dest_before} to past event-location  # verbosity
	set {_dest} to past event-location
	set x-pos of {_dest} to (x-pos of {_past}) * 8
	set z-pos of {_dest} to (z-pos of {_past}) * 8
	set world of {_dest} to world("smp")
	set event-location to {_dest}
	broadcast "Dest before: &c%{_dest_before}%"  # verbosity
	broadcast "Dest after : &a%event-location%"  # verbosity

Results before the change:

Results after the change:

skript-portal-poc.mp4

Supporting Information

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Completes: none
Related: #5624

[Absolutionism]

I think these should be moved to EvtMoveOn