Feature/wdboggs/#4292 test verticalgrid aspect

[darianboggs]

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 implements tests for the update_payload and update_from_payload methods for the VerticalGridAspect type.

Related Issue

#4292

[darianboggs]

Because of the complexity with VerticalGrid, VerticalStaggerLoc, VerticalAlignment variations (each present or not present), this PR focuses on VerticalGrid. The other variations can be implemented in a subsequent PR.