WCS SD Tile transformation incorrect

[christinawlindberg]

It looks like the tile transformation from RA/DEC to x/y isn't correct when figuring out which tiles fall within the boundary region in make_ast_xy_list.py around lines 286. I noticed this since there were edge tiles in high source density bins that clearly overlapped the boundary area in RA/DEC, resulting in 4 non-empty source density map bins, but when the code actually ran, only 3 non-empty map bins were filled.

Currently, the boundary and tile overlap in make_ast_xy_list.py is checked in xy coordinates. If the same check is made with RA/DEC coordinates, then the edge tiles remain and aren't removed, resulting in 4 non-empty map bins.