Update `load_model` to read from `*.outbin` file

[lawrenceabird]

Currently, pyissm.model.io.load_model() requires that ISSM models be saved as a *.nc file. Natively, ISSM outputs an *.outbin file.

load_model() should be updated to load directly from an *.outbin file.

Requiements:

• Generate a read_outbin() function that maps the *.outbin file to the ISSM Model() class.

Review $ISSM_DIR/scripts/OutbinRead.py as a starting point.

[lawrenceabird]

It's not appropriate for the load_model() function to pull from the *.outbin file. This file only contains model results.

To load a model from binary files, it's necessary to construct the Model() object from both the *.bin (inputs) and the *.outbin (outputs) files.