[cpp] Better skillup handling with sch arts active

[MowFord]

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What does this pull request do?

Closes #1981 .

Steps to test these changes

at 0 skill enf with dark arts was at 246, skilled up and it stayed the same:

at 200 real skill, dark arts put me to 246. Skillup put me to 247:

[zach2good]

I dont know anything about SCH, but what this says to me is that we're going to call BuildingCharSkillsTable whenever TrySkillUP is called - presumably on every action or melee swing etc. if ArtsBonusActive is on.

There's no DB calls in there, it's just a bunch of math, that seems OK, but logically: when ArtsBonusActive falls off, shouldn't we be rebuilding the table one more time to put it back at its original non-inflated state?

[MowFord]

there's actually more work done when light/dark arts is gained/lost (in onEffectGain/onEffectLose)

and this is only going to do the extra math if the skillup in question is relevant to the currently-active arts buff. Perhaps that function could be renamed for clarity, but it returns true if SkiiID is one of the skills boosted by a current arts effect