Blender Git Loki

UDIM: Fix tile number calculation when adding a range of image tiles

When adding a range of tiles, the operator could incorrectly calculate
the end_tile. It would not account for the start_tile itself and the
IMA_UDIM_MAX value was 1 too small. This is most noticeable when
attempting to fill the entire supported range of tiles.

Differential Revision: https://developer.blender.org/D11857