Need: a unified way of making meshes

[adrifoster]

We have realized that many of us (me, @slevis-lmwg, @swensosc, etc.) use different methods to create mesh files to run with the new NUOPC coupler.

It would be good to figure out how those methods are different/similar and create a unified method.

Currently, we need a mesh creation script that can handle global, regional, and "sparse" grids for our use cases. The current mesh_maker script has some bugs associated with it, and I don't think would work for the sparse grid scenario.

Some issues we know of related to mesh maker/mesh creation:
#2774
#2776
#1731