[c2cpg] Added fullname uniqueness for type decls, bindings, and namespace blocks

[max-leuthaeuser]

No description provided.

[maltek]

I was going to caution that we need to preserve the links from a class with forward-declared member functions (usually in header files) to the implementations of those functions (usually not in headers). But I can't actually find any such links (e.g. method bindings) as of yet. So we'll just have to be careful about all that once we implement it.

class A {
    int foo();
}

#include "a.hpp"

int A::foo() {
    return 1;
}

[max-leuthaeuser]

I was going to caution that we need to preserve the links from a class with forward-declared member functions

We never create methods or bindings for forward-declared methods if we encounter an actual implementation later on.

[maltek]

We never create methods or bindings for forward-declared methods if we encounter an actual implementation later on.

Yes, that's what I was trying to say. We should at some point (once we also emit proper dynamic calls), but that's for another PR.