Fixes #2553. Detect mpiuni builds of ESMF

[mathomp4]

Description

This PR adds a check in Cap after ESMF_Initialize to see if ESMF was built as mpiuni which is not supported by MAPL (we require "real" MPI). Thanks to @oehmke, ESMF_VmGet can tell us the comm.

Related Issue

Closes #2553

Motivation and Context

It was found that a GCHP issue could have been quickly diagnosed if this assertion was in MAPL.

How Has This Been Tested?

Currently testing to make sure GEOSgcm runs. It should, but good to be safe.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Trivial change (affects only documentation or cleanup)

Checklist:

• I have tested this change with a run of GEOSgcm (if non-trivial)
• I have added one of the required labels (0 diff, 0 diff trivial, 0 diff structural, non 0-diff)
• I have updated the CHANGELOG.md accordingly following the style of Keep a Changelog