TreeMaker should not call type() on pointer types too early

The jextract parser deals with pointers using some logic to handle circular references - e.g. cases like:

struct A {
    B *ptr_b;
};

struct B {
   A *ptr_a;
}

In such cases, the types *A and *B are added to a list of unresolved type, which is then only fixed up at the end of parsing. For this reason, it is only safe to obtain the pointee type of a pointer type only after parsing. Unfortunately TreeMaker has some calls to DelegatedType::type() which, under the right conditions can cause issues because of this lazy completion system.