[clang] [clang] Diagnose dangling issues for the "Container<GSLPointer>" case. (PR #107213)

[Haojian Wu via cfe-commits]

hokein wrote:

Thanks, it looks like this introduces a new false positive:

```
#include <optional>
std::optional<int*> func(int a) {
  if (a)
   return std::make_optional(nullptr); // emit a dangling.
}
```

I'm going to revert it.

https://github.com/llvm/llvm-project/pull/107213