Small fixes to run this code in 2023

[esgn]

I don't know if the code is still maintained but here are several small fixes I introduced to try and run it without CGAL bindings. Putting them here if it can help.

As the libraries versions are not fixed, I stumbled upon compatibilities issues with newer versions of them.

• Numpy has deprecated np.bool since 1.24.0. I replaced it with bool as it seems np.bool was only an alias on Python bool type
• Shapely MultiPolygons need to be accessed through .geoms to iterate over them
• Shapely cascaded_union is deprecated and will soon be replaced by unary_union

I also added two checks to prevent what seem to me as unnecessary breaking exceptions:

• In compute_shape() in fit.py I noticed that when @Geodan/concave-hull returns an invalid polygon (it does happen from time to time) the union will break. Added a check to prevent merging alpha shape geometry with invalid concave-hull geometry
• In triangle_geometry() in alpha_shape.py I encountered some cases where sqrt() had to deal with a very small negative number. I added a try: ... except ValueError: ... around it and initialized the area value to 0