[clang] [clang][Sema] Fix a bug when instantiating a lambda with requires clause (PR #65193)

[via cfe-commits]

cor3ntin wrote:

There is also the question of what happen in the deeply nested case

```cpp

void f(auto a) {
   [] {
           [] () requires requires foo(a) {}();
   }();
}
```

we may have to visit all functions recursively from the bottom up to add their locals / parameters / captures



https://github.com/llvm/llvm-project/pull/65193