[DirectVerbs] Add support to Spectrum MPI

[pakmarkthub]

Problem:

• When using Spectrum MPI, we need to link against libmpi_ibm instead of libmpi.
• This project cannot be compiled because it hard-code with -lmpi.

This PR:

• adds --with-spectrum-mpi to configure. When it is detected, -lmpi_ibm will be used instead of -lmpi.
• adds check that --with-mpi and --with-spectrum-mpi settings are mutually exclusive.

Presubmit testing:

• Called configure and make on Summit and verified that the project can be compiled with Spectrum MPI.