OpenMPTarget backend general issue

[lucbv]

Kokkos has made significant progress including hierarchical parallelism and atomics. At this point it is worth tracking Kokkos remaining progress and starting to test it in Kokkos Kernels.
This backend is intended to be generic to GPU accelerators so it can be tested on Kokkos-dev2 with Cuda, on caraway or Tulip with HIP and on Iris with oneapi.

Here is a list of the current and planned tasks needed for us to complete this backend (this will evolve over time so check it back regularly for progress).

• Track remaining issue in Kokkos, see issue Kokkos #3710
• Enable OpenMPTarget and OpenMPTargetSpace through CMake and ETI, see issue OpenMPTarget: CMake and ETI #891 and PR OpenMPTarget: adding ETI and CMake logic for OpenMPTarget backend #886
• Add preprocessor for GPU to have generic code path (instead of check each GPU space) and modify helper functions
• Refactor testing infrastructure and enable test for this backend
• Update cm_test_all_sandia, setup nightly builds and auto-tester builds
• Update Spack package