Inlay hint for package imports

## Is your enhancement request related to a problem? Please describe.

When looking at an import, it's not obvious at a glance what package it comes from.

## Describe the solution you'd like

There is a syntactically valid way to show what packages imports come from: `PackageImports`! So we can have inlay hints where inserting the inlay hints gives valid Haskell, which is quite nice.

Something like this:
```
import "base" Data.List
```

## Describe alternatives you've considered

We already show packages and versions when hovering on imports, but this makes it even more immediate. It's probably going to be a bit of a love-it-or-hate it thing. And `PackageImports` is I think "discouraged" so maybe we shouldn't be encouraging people to use it.