Fix fields utils, Issue #2530

[darianboggs]

Description

This feature PR adds the npes to the @Test decorators. It also moves creation of some fields to the test subroutines so that the field creation is consistent with the regDecomp argument.

Related Issue

#2530

Motivation and Context

npes were not being passed into the test subroutines.

How Has This Been Tested?

Ran the MAPL tests in question

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