[ntuple] Members of an aliased type do not resolve to the underlying type

- [X] Checked for duplicates
### Describe the bug
```c++
namespace SG { typedef uint32_t sgkey_t; }
class X {  SG::sgkey_t  sgkey = 123; };
```

Produces the same error: "Field sgkey has unknown type SG::sgkey_t"

Cheers, Marcin.

### Setup
Using ROOT from `master` branch.