fix non-finite yaw/pitch issue, clean ExprYawPitch, and remove VectorMath

[sovdeeth]

Problem

Exception thrown when setting yaw/pitch to non-finite values

[18:18:53 ERROR]: #!#! Stack trace:
[18:18:53 ERROR]: #!#! Caused by: java.lang.IllegalArgumentException: pitch not finite
[18:18:53 ERROR]: #!#!     at org.bukkit.util.NumberConversions.checkFinite(NumberConversions.java:124)
[18:18:53 ERROR]: #!#!     at org.bukkit.craftbukkit.entity.CraftEntity.setRotation(CraftEntity.java:270)
[18:18:53 ERROR]: #!#!     at Skript-2.13.2.jar//ch.njol.skript.expressions.ExprYawPitch.changeForEntity(ExprYawPitch.java:117)

Solution

Don't change if value is non-finite. Also removes VectorMath as it has been deprecated since 2.10, plus a few other minor touchups to ExprYawPitch

Testing Completed

Added a regression test.

Supporting Information

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Completes: none
Related: none
AI assistance: none