Canopy roughness parameterization modular

[kmdeck]

Purpose

Our default sets roughness lengths for the canopy as parameters using the toml. In almost all our example, though, we override these by using a constant times the canopy height. This PR updates the default so that it does what we want

This also creates a roughness parameterization struct which we can dispatch off of when computing surface fluxes. Since the shared canopy parameter struct then only has the earth param set, we can remove that from our code; this also enables us to change roughness paramterizations in the future

Closes #1351

To-do

Content

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