`U1, U2, ...` are usable as types but not as parameters

They are defined as `type Uxyz = Const::;`

When you need to pass it as a generic parameter this works.

But there are some functions (`reshape_generic` for example) that take `Const::, Const::` in their function arguments, as a way to avoid the turbofish, as rust can deduce the type arguments from the function arguments.

However in this position we can't use `U1, U2, ...`

You get an error
```
error[E0423]: expected value, found type alias `na::U12`
```

Can we have `const`s with the same name so `Uxyz` can be used as a value as well?