[Libomptarget] Rework device initialization and image registration (#93844)

Summary:
Currently, we register images into a linear table according to the
logical OpenMP device identifier. We then initialize all of these images
as one block. This logic requires that images are compatible with *all*
devices instead of just the one that it can run on. This prevents us
from running on systems with heterogeneous devices (i.e. image 1 runs on
device 0 image 0 runs on device 1).

This patch reworks the logic by instead making the compatibility check a
per-device query. We then scan every device to see if it's compatible
and do it as they come.