Common global convergence meshes

[xylar]

This has meshes that can be reused by multiple subsequent test cases. The cosine bell test cases have been updated to use meshes created in the ne meshes test case.

This work is in anticipation of using the same meshes for cosine_bell and geostropic (Williamson Test 2) test cases.

Checklist

• [ ] User's Guide has been updated
• [ ] Developer's Guide has been updated
• [ ] API documentation in the Developer's Guide (api.md) has any new or modified class, method and/or functions listed
• [ ] Documentation has been built locally and changes look as expected
• [x] Testing comment in the PR documents testing used to verify the changes
• [x] New tests have been added to a test suite
• [ ] Cache files have been updated

[xylar]

Testing

The 4 cosine bell test cases pass on Chrysalis and the outputs are BFB with main after this reorganization.

[cbegeman]

@xylar Great! It occurred to me that this would be handy when I was working on the sphere_transport test group. I see this is marked as draft; would you like me to review and/or test now?

[xylar]

@cbegeman, why don't you hold off for now. I need to update the docs and I already did sufficient testing aI think.

You are certainly welcome to take a quick glance, though, and let me know if something looks significantly off compared to what you had been thinking of. That high-level review would be useful before I get too far with the docs.

[xylar]

I'm going to close this until we do the reorganization in #109