[style-guide] Parameter owner patterns should be consistent with prefix application expressions

Union cases patterns should be consistent with their creation expressions, like this:
```fsharp
let _ = Foo x
let _ = Bar(1, 2)

match s with
| Foo x -> ()
| Bar(1, 2) -> ()
```

Currently Fantomas adds an extra space in the last pattern, which makes it inconsistent. I propose we should fix this.

Start by locating Fantomas's handling of union-case creation and pattern expressions, then compare the formatting paths for `Foo x` and `Bar(1, 2)` shown in the issue. Confirm the current output and identify the relevant formatter tests; done means parameter-owner patterns use the same spacing as their corresponding creation expressions.

Written by the indexing model from the issue text.