[ClimaCoreTempestRemap] Support for terrain-warping in NetCDF output

[simonbyrne]

Is your feature request related to a problem? Please describe.
Terrain export is not currently supported (CliMA/ClimaAtmos.jl#536)

It should adhere to the CF conventions, e.g.
https://cfconventions.org/Data/cf-conventions/cf-conventions-1.9/cf-conventions.html#atmosphere-hybrid-height-coordinate

Describe the solution you'd like
Add method to def_space_coord that supports this. It may also require modifying how we internally represent the space.

Describe alternatives you've considered
CliMA/ClimaAtmos.jl#536 does a quick hack to support it, but the results will not be correct (i.e. each level will have the same z values)

Additional context