Addressing the MPI wrappers and GTL support technical debt

[pearce8]

mpicc (mpi compiler wrapper) needs to be used for linking

• @scheibelp Please find an example of a benchmark which correctly uses the MPI compiler wrapper, and point it out here as a good example for how CMake and package.py should work
• amg2023
• kripke
• Laghos
• RAJAPerf
• To test GTL, export MPI_GTL_SUPPORT=1. Need to check if linking the appropriate libraries -- probably need to check all of our benchmarks as well