[WIP] Initial attempt at basic Terrarium extension

[bgroenks96]

This is an initial very rough attempt at creating an extension module for Terrarium.

I think for now we can get away with just assuming that the land grid always matches the exchange_grid thus avoiding any need for regridding.

Prerequisities:

• Register Terrarium
• Add Land submodule and component in EarthSystemModel (see Add land as a top-level EarthSystemModel component #36)

[codecov]

Codecov Report

❌ Patch coverage is 0% with 35 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../NumericalEarthTerrariumExt/terrarium_exchanger.jl	0.00%	21 Missing ⚠️
...calEarthTerrariumExt/terrarium_land_simulations.jl	0.00%	14 Missing ⚠️

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