[clang] [Clang] Fix name lookup for dependent bases (PR #114978)

[Krystian Stasiowski via cfe-commits]

https://github.com/sdkrystian commented:

I don't think this patch fixes the following case:
```cpp
template<typename T> 
struct A 
{
    struct B 
    {
        using X = int;

        struct C
        {
            using X = void;

            struct D;
        };
    };
};

template<typename T> 
struct A<T>::B::C::D : B
{
    X x; // error: field has incomplete type 'X' (aka 'void')
};
```
Regardless, this patch should probably this as a test.

https://github.com/llvm/llvm-project/pull/114978