Fixes NBT-Data Leak from Spell Circle Looping

[Stick404]

In 1.20 Spell Circles can loop on their own slate, however this can cause massive NBT-Leaks due to the same positions stacking on the same positions. This PR just makes reachedPositions a HashSet/Set, and adds an extra Int Var of "reachedNumber", or how many slates it has come across (this is for the speed up of Spell Circles).