Unify integer constants between mpi.h and the Fortran interfaces

[jsquyres]

Per discussion in #10491, OMPI currently has two sources of truth for public integer constants:

1. mpi.h.in
2. mpif-values.pl (a script which writes out Fortran source files that get included by the various Fortran interfaces)

A lot of MPI constants are hard-coded to the same integer values in both places.

• Note that there are a few weird cases, such as the C values MPI_F_SOURCE, MPI_F_TAG, and MPI_F_ERROR which correspond to the Fortran values (MPI_SOURCE-1), (MPI_TAG-1), and (MPI_ERROR-1)

This dual-source-of-truth strategy has been "good enough" for a long time, but it's error prone, and it has caused bugs in the past (e.g., where the C value was X and the Fortran value was Y, or where the C value was X and it wasn't defined in Fortran). We really should unify the integer constant values between mpi.h and the public Fortran interfaces so that there is a single source of truth for all of these integer values.