add ClimaCoupler downstream test

[juliasloan25]

Purpose

It would be useful to have a driver that runs a simple coupled ClimaAtmos/ClimaLand setup for one or two timesteps. This could be used by these packages to test the effects of changes downstream in ClimaCoupler. It wouldn't test physical stability, but it would test interface changes

see https://github.com/CliMA/ClimaCoupler.jl/issues/877

To-do

It would be good to have a more streamlined test that doesn't require instantiating the entire ClimaEarth environment, but for now this is fine

Content

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