Feature/stefan concat input

This draft PR combines a handful of features

Modify preprocess.py to optimize intermediate numpy files, partially closes https://github.com/NOAA-PSL/model_error_correction_with_ai/issues/#28 and partially closes https://github.com/NOAA-PSL/model_error_correction_with_ai/issues/#27
modify training related codes to work with new files
modify training codes to be more efficient with new files (avoid striding)
point code to the new location of files on hera

NOAA-PSL / model_error_correction_with_ai