Enhance vx_data_ugrid library to read in tripolar projected datasets

Describe the Enhancement

Due to its non-standard gridding methodology (i.e. inconsistent distance between latitude and longitude lines), tripolar projection is unable to be utilized by any of MET's tools. This has historically meant that tripolar projection datasets cannot be used in any way in MET. However if the tripolar projection is approached as a system of points, we can then use a k-d tree distance method for analyzing the tripolar "grid" points and point observations. This methodology would open up the ability to verify tripolar projected forecasts with point observations in tools like Point-Stat.

To do this, we will need to enhance the vx_data_ugrid library to support this new projection.

The work in this issue is the point-verification side of #2658, which will deal with the grid-verification (including interpolation).

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Define Related Issue(s)

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[ ] METplus, MET, METdataio, METviewer, METexpress, METcalcpy, METplotpy

Enhancement Checklist

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dtcenter / MET