Calibrate ClimaLand: single site mwe

[AlexisRenchon]

In a first step toward ClimaLand calibration, we add a minimal working example to calibrate parameters at a single site (single column). This example aims to be as simple and readable as possible.

First, we calibrate on a previous model run, to demonstrate that we can recover the original parameters with the implemented calibration framework. Second, we calibrate on actual data, to demonstrate improved model-data agreement after calibration.

We use the Ozark Fluxnet site data, and calibrate the parameters g1 and g0 on evapotranspiration.

Following this PR, another one will add a simple calibration demonstration on global run.

PR: #621