[clang] Reapply "[clang] Fix name lookup for dependent bases" (PR #118003)

[Yanzuo Liu via cfe-commits]

================
@@ -1178,17 +1178,61 @@ namespace cwg590 { // cwg590: yes
   template<typename T> typename A<T>::B::C A<T>::B::C::f(A<T>::B::C) {}
 }
 
-namespace cwg591 { // cwg591: no
+namespace cwg591 { // cwg591: yes
----------------
zwuis wrote:

```suggestion
namespace cwg591 { // cwg591: 20
```


https://github.com/llvm/llvm-project/pull/118003