unboxedSum{Type,Data}Name: Use GHC.Types as the module

Unboxed sum constructors are now defined in the `GHC.Types` module, so if you
manually quote an unboxed sum (e.g., `''Sum2#`), you will get a `Name` like:

```hs
GHC.Types.Sum2#
```

The `unboxedSumTypeName` function in `template-haskell`, however, mistakenly
believes that unboxed sum constructors are defined in `GHC.Prim`, so
`unboxedSumTypeName 2` would return an entirely different `Name`:

```hs
GHC.Prim.(#|#)
```

This is a problem for Template Haskell users, as it means that they can't be
sure which `Name` is the correct one. (Similarly for `unboxedSumDataName`.)

This patch fixes the implementations of `unboxedSum{Type,Data}Name` to use
`GHC.Types` as the module. For consistency with `unboxedTupleTypeName`, the
`unboxedSumTypeName` function now uses the non-punned syntax for unboxed sums
(`Sum<N>#`) as the `OccName`.

Fixes #24750.