[metacling] Handle autotypes in collect_type_info

[aaronj0]

In CallFunc, we canonicalise types before collecting their typeinfo and names. However, if we have an alias to a template type which uses a private struct, this causes us to lose the sugar that makes the type accessible since the struct is private.

template<class T>
class Container {};

class Foo {
private:
   struct Tag;
public:
   using iterator = Container<Tag>;

   auto begin() {
       return iterator{};
   }
};

calling begin on an instance of Foo gives us:

extern "C" void __cf_12(void* obj, int nargs, void** args, void* ret)
{
   if (ret) {
   // CallFunc does:
   // new (ret) (Container<Foo::Tag>) (((Foo*)obj)->begin());

   // What should be used:
      new (ret) (Foo::iterator) (((Foo*)obj)->begin());
      return;
   }
   else {
      (void)(((Foo*)obj)->begin());
      return;
   }
}

This PR should fix #18837 (will add tests)

[github-actions]

Test Results

    20 files      20 suites   3d 22h 11m 5s ⏱️
 3 042 tests  3 041 ✅ 0 💤 1 ❌
59 056 runs  59 054 ✅ 0 💤 2 ❌

For more details on these failures, see this check.

Results for commit 1397502.

[pcanal]

Can you add a test? Thanks.