Fix naming convention for stdlib.

[weinbe58]

Some ideas here:

• To indicate the starting/ending points of a move use src and dst respectively
• Integer indices into grids: row and col to represent rows and columns of the grid respectively
• Positions indicated via x and y for physical coordinates in floating point values

Because this could be breaking some of the current APIs we should go through and make sure the standard libraries are following these naming conventions before we migrate to Kirin 0.20

cc: @WanHsuanLin