translate spinup stability script to python

[djk2120]

There are some existing ncl scripts for assessing spinup stability in tools/contrib. There are a view key reasons that it might be nice to have this available as a python tool.

1. deprecation of ncl
2. python (dask) would allow parallelization which would make processing monthly data faster
3. we can use yaml files to configure stability thresholds without editing the script
4. I've found with python I can easily parse the stability status for automated spinup workflows

I have an existing script for this that I'll put in a PR, but it's probably still missing a couple of things that could be beneficial (e.g. unstructured grids)

[ekluzek]

Oooh, @djk2120 excellent! The spinup stability script is so crucial to the process that I've long wanted to see this happen. But, we also knew that doing it would take effort. But, if you have a start at this, that would be so helpful. This would be a great thing to add to the b4b-dev branch, and once there we'll be able to make modifications to it and extend it's behavior.

Longer term once it's in python, we'd also add some testing around it, and make sure it goes nicely in our python code structure.

Cool, thanks for letting us know about this. This is good news to have just before a weekend.

[djk2120]

This code is included in my tether draft PR (#3459), but has been separated into its own folder as a separate tool