Update GraphCast scripts from DeepMind repository

The GraphCast scripts on DeepMind's repository got significant updates that should be applied to the EMC GraphCast repository. Updates include:

Updating Readme
Dependencies version update
updates on data_utils.py and data_utils_test.py
updates on casting.py
updates on the normalization.py script
updates on the rollout.py script
updates on xarray_jax.py
updates on graphcast_demo.ipynb
added scripts for calculation of top of atmosphere solar radiation in case of operational use
some other minor scripts updates

NOAA-EMC / graphcast