Add spherical correction terms

[kgoebber]

Description Of Changes

So this is a first attempt to get in the spherical correction terms as discussed in #893. List of calculations modified:

• vorticity
• absolute vorticity
• divergence
• stretching deformation
• shearing deformation
• total deformation
• frontogenesis
• potential vorticity baroclinic
• inertial-advective wind
• q-vector

These changes are effective for global datasets that use a lat/lon coordinate. In some testing with NAM data, the correction is not needed or will need a different type of correction. I'll update the issue with a bit more information about this for the ongoing discussion.

Current implementation adds latitude to the list of keyword arguments for affected calculations (some already had it) and a flag for whether to apply the spherical correction (default to True). The reason to default to True is that users are more likely to need it. It would be best if we could programmatically figure out if it is needed based on the CRS, but this placeholder will do for this initial draft of a PR. Therefore, I did not add documentation about the spherical_correction keyword argument figuring we can wait to see how the final implementation goes.

I updated some of the tests where we won't want the correction (made up data that is not associated with lat/lon values). A number of tests will fail as I have not attempted to go through and update values based on the corrected calculations.

We should add some tests based on a non-GFS actual data file (e.g., NAM) for these specific calculations.

Checklist

• Partially Closes Generalize vorticity (and related functions) to allow for map projections #893
• Tests added
• Fully documented

[kgoebber]

Completed via #2743. Closing this old PR.