Add support for methods in namespaces

[Discusser]

When using TSCppDefineClassFunc on a method inside of a namespace, the function should be defined with the namespace.
Example header file:

namespace A {
void b();
class C {
  void d();
  C e(C param);
};
}

Expected output when using TSCppDefineClassFunc:

void A::b() {}
void A::C::d() {}
A::C e(C param) {}

Currently, this just outputs the following (notice the lack of namespaces):

void b() {}
void C::d() {}
C C::e(C param) {}