Since FPHSA is called for multiple compiler languages with "MPI_${lang}"
rather than just "MPI", make sure variables for controlling QUIET,
REQUIRED and VERSION are propagated with names prefixed by MPI_${lang}
as well, rather than just MPI.

The find_package call sets up the values of MPI_FIND_REQUIRED and friends,
but these calls to FPHSA need MPI_${lang}_FIND_REQUIRED and friends in
order to function as intended.