Add workaround for qualified record extension

This code does not parse in elm-compiler:

```elm
{ SomeModule.base | x = 1 }
```

elm-format could detect code like that and replace it with:

```elm
let
base = SomeModule.base
in
{ base | x = 1 }
```

Start by locating elm-format's handling of record extension expressions and how it represents qualified expressions. Reproduce the elm-compiler parse failure with `{ SomeModule.base | x = 1 }`, then verify that the formatter produces the shown let-binding workaround while preserving the resulting record update.

Written by the indexing model from the issue text.