lib: some update towards more use of new constructors

Signed-off-by: Jean Privat <privat@pryen.org>
modelize: simplify special-case for named constrcutors

The only remaining case is for old style init named "init" since they
need a move clever transition scheme.

Signed-off-by: Jean Privat <privat@pryen.org>
tests: update related to the init changes

Signed-off-by: Jean Privat <privat@pryen.org>