astbuilder: Make the construction of the `AMethPropdef` more generic
astbuilder: Make the construction of the `AMethPropdef` more generic

Change the MMethodDef to nullable MMethodDef to reduce model dependency.

Change the APublicVisibility to AVisibility to be able to create private or protected method.

Signed-off-by: Florian Deljarry <947961b90cb93a9343e8ca0457b9d463c3e20c1c@gmail.com>
privat/nit,privat/nit,privat/nit,privat/nit,privat/nit,privat/nit,privat/nit,privat/nit,privat/nit,privat/nit