Kind equalities changed how `*`/`#` are represented internally, which
means that showing a `TypeRep` that contains either of those kinds
produces a rather gross-looking result, e.g.,

```
> typeOf (Proxy :: Proxy 'Just)
Proxy (TYPE 'Lifted -> Maybe (TYPE 'Lifted)) 'Just
```

We can at least special-case the `Show` instance for `TypeRep` so that
it prints `*` to represent `TYPE 'Lifted` and `#` to represent `TYPE
'Unlifted`.

Addresses one of the issues uncovered in #11334.

Test Plan: ./validate

Reviewers: simonpj, hvr, austin, goldfire, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1757

GHC Trac Issues: #11334