Kripke stand-alone umpire build

[rfhaque]

This PR adds an Umpire-only build to Kripke

1. If ENABLE_CHAI=ON, then the code builds as before using both CHAI and Umpire.
2. If ENABLE_CHAI=OFF, but either ENABLE_CUDA=ON or ENABLE_HIP=ON, i.e. for a GPU build, the code builds an Umpire-only version with a device pool. It is important to note that an Umpire-backed CPU build is only possible when using CHAI (as before). A standalone CPU-only Umpire-only build is NOT supported
3. When ENABLE_CHAI=ON, the cmake config enables two pragma definitions KRIPKE_USE_CHAI and KRIPKE_USE_UMPIRE
4. When ENABLE_CHAI=OFF, but either ENABLE_CUDA=ON or ENABLE_HIP=ON, the cmake config enables only KRIPKE_USE_UMPIRE
5. The logic to manage the memory HtoD or DtoH memory transfers is implemented in the file Field.h. As with CHAI, the Umpire-only allocation only allocates storage for an execution space if the code actually touches the data on that space.

[rfhaque]

@pearce8 Please review