Fix selection of ttype field on ir.model.fields
Fix selection of ttype field on ir.model.fields

Replace the method by a the use of `selection_add` in order
to allow other modules to extend the list of field type.

Otherwise, it would crash on when installing for instance
both base_geoengine and base_sparse_field.

OCA/geospatial,OCA/geospatial,OCA/geospatial