cubicweb #2793792 Add a "cw_type" attribute/property to AnyEntity [validation pending]

For now, dc_type cannot be used (since it's i18n'ized), and using __regid__ as official public API to get this information is not so nice (so to speak).

prioritynormal
typeenhancement
done in3.17.0
load0.250
load left0.000
closed by#c7a95ebcc093 [entity] add an official ``cw_etype`` property for entity
patch[entity] add an official ``cw_etype`` property for entity [applied]