[clang] [clang] Substitute alias templates from correct context (PR #74335)

[Mariya Podchishchaeva via cfe-commits]

Fznamznon wrote:

Thanks, I reproduced the problem with
```

template <typename T> class shared_ptr {
    T* data;
};

template <typename Tfs> class cfftpass {
    static shared_ptr<cfftpass> make_pass();
};

template<typename T> using Tcpass = shared_ptr<cfftpass<T>>;

template<typename Tfs> Tcpass<Tfs> cfftpass<Tfs>::make_pass() { return Tcpass<Tfs>{};};                                                                   
```

https://github.com/llvm/llvm-project/pull/74335