Remove global mutable fields and reduce data-type related duplication

[kyay10]

• Use Vecx instead of FloatArray
• Add Vec3Setter and Vec4Setter, function types that encode placing a value inside a VecX or FloatArray
• Eliminate usage of global mutable fields like _f and _b and withX and instead use mutableReference/mutablePropertyAt
• Get rid of previous erroneous MutableProperty implementation (the getter was constant, so it wouldn't reflect setter) and replace it with a factory function
• Unify and rename widgetType-style functions (e.g. sliderInt) to reduce duplication
• Add NumberOps interface along with associated methods to facilitate generic math operations
• Remove dataTypeHelpers.kt and instead add them as functions on NumberOps
• Remove PlotArray and replace it with an inline lambda
• Change some KMutableProperty0 into plain values. This fixes a bug where min/max values were swapped by functions and affected the outside (Which is a misinterpretation of the C++ version. See this for an explanation of ImSwap behavior)
• Extract common elements of dragN, inputN, and sliderN into a widgetN function.
• Remove MutableProperty0.java and instead use MutableReference
• Fix refCol usage in colorPicker4

For the future: Maybe we should also remove the overloads that take an array and a ptr and call mutablePropertyAt? It's useless duplication because the user can just call mutablePropertyAt on their own.

[elect86]

Thanks for the PR

For the future: Maybe we should also remove the overloads that take an array and a ptr and call mutablePropertyAt? It's useless duplication because the user can just call mutablePropertyAt on their own.

That actually makes sense..