Add the inverse APIs to the existing discrete-property setters:
- case.property_data_type(property_type, property_name) returns "FLOAT" or
"INTEGER", matching the data_type flag passed to set_active_cell_property
/ set_grid_property.
- case.discrete_property_category_names(property_name) and
case.discrete_property_category_colors(property_name) return the
{int: str} mappings previously bound via
set_discrete_property_category_names, or empty dicts when nothing is bound.
Implemented as PdmObjectMethods on RimEclipseCase and
RimColorLegendCollection so the bindings surface automatically through
generated_classes.py.