Memory policy

[nksauter]

I've created a failing unit test for new kokkos code in the cuda-context.

If the test "libtbx.python cctbx_project/simtbx/tests/tst_memory_policy.py" can be made to work, the bug has been fixed.

Background information: I'm trying to extend the kokkos exascale_api with new behavior. In the old way, it would allocate large arrays on GPU corresponding to the detector size even if only a few pixels are calculated due to the whitelist (a list of pixels of interest). In the new behavior only enough memory is allocated for the whitelist pixels. I am using C++ templates with template specialization dependent on these two memory-allocation cases. I need this to work so Daniel can move ahead with the SPREAD project, and it is just this last detail that I cannot seem to fix.