[Refactoring]: Internal Hex Grid Coordinate Change

[ColdAnkles]

Describe the problem

Discussion in #4886 revealed some distaste for the offset coordinate system used by MapTool for hex grids. (off-q, or off-r)

The improvement you'd like to see

It is suggested to move to cubic coordinates instead of offset.

Expected Benefits

This should simplify the java side coordinate math, since no offset maths would be required any longer, and vectors would just work.
Display coordinates could then be implemented for graphs, allowing for options such as the existing offset system, cubic, or axial.
Also allowing for y-up instead of the current y-down.

Additional Context

Coordinate vector math would also no longer need to care about handling offsets wherever it is - entities dealing with coordinates don't care about the grid and what offset it is.