Update to extdata2g compatibility with non-CF inputs

[tclune]

Types of change(s)

• 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)
• Refactor (no functional changes, no api changes)

Checklist

• Tested this change with a run of GEOSgcm
• Ran the Unit Tests (make tests)

Description

This PR has a minor change in the criteria for determining if a non-CF file vertical dimension is positive up or down based on lev dimension attributes when using ExtData2G. Previously standard_name was used. However, I discovered that standard_name is not present in the processed GEOS-FP file used in GCHP. We do have long_name present across all of our processed meteorology input files so made this PR to change standard_name to long_name for the criteria. This should not impact GEOS users since the code block to check direction in non-CF files was introduced by me for GCHP.

Related Issue

Supersedes #4787 (rebased from geoschem/MAPL fork to allow merge)

[tclune]

@lizziel