Enhance Pair-Stat to support Ioda and Python inputs and refine masking logic

[JohnHalleyGotway]

Describe the Enhancement

#3006 added the initial version of the Pair-Stat tool for the MET-12.1.0-beta1 release. This issue is to extend the functionality of Pair-Stat as described below:

• Add support for the -format ioda and -format python command line options.
• Provide a way to filter data by time.
• Refine the way spatial masking is handled. Currently, all grid and poly masks are mapped to a global 1/10 degree grid, but leads to inconsistent application of masking regions at the edges. Instead, let the grid vary for each masking region.
  Complete the documentation for this new tool.

Time Estimate

~ 1 week?

Sub-Issues

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None needed.

Relevant Deadlines

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Define Related Issue(s)

Consider the impact to the other METplus components.

• METplus, MET, METdataio, METviewer, METexpress, METcalcpy, METplotpy
  No impacts expected.

Enhancement Checklist

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• Complete the issue definition above, including the Time Estimate and Funding Source.
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