Add a data_type parameter to set_active_cell_property, set_active_cell_property_async
and set_grid_property so callers can upload INTEGER-typed discrete properties in
addition to the existing FLOAT properties. Previously a discrete property required
the result name to end with "NUM"; the explicit data type makes the intent
independent of the name.
The gRPC service now forwards the selected data type to
RigCaseCellResultsData::createCategoryResult, and the Python tests cover both
float and integer property uploads.