Faulted Earth: Re-write the fault geometry utility with hazardlib

[Lars Butler]

There's a utility currently implemented with OpenSHA (java) and jpype. We should re-write this with hazardlib.

Note: Due to implementation differences, the results will probably be slightly different.

The function is here: https://github.com/gem/oq-platform/blob/08ec1b47b905d5acb04287d786bc4a030d4277c7/openquakeplatform/openquakeplatform/faulted_earth/models.py#L408

The geometry for this class (`simple_geom`) is a MultiLineString. It seems, however, that it can possibly contain only 1 linestring. My guess is that a single linestring represents a simple fault, while a multi linestring represents a complex fault. If this is correct, this hint will help guide the implementation.