[SourceKit/CodeFormat] Column-align enum element decls and the items in their parameter lists.

[nathawes]

I missed this in the initial indentation rework. It wasn't handling them at all so we ended up with multi-line enum case decls like the below:

enum Foo {
    case first,
    second
    case third(a: Int,
    b: Int),
    fourth(a: Int,
    b: Int
}

which is a regression compared to the slightly better 5.2 behavior:

enum Foo {
  case first,
  second
  case third(a: Int,
    b: Int),
  fourth(a: Int,
    b: Int)
}

New behavior is:

enum Foo {
  case first,
       second
  case third(a: Int,
             b: Int),
       fourth(a: Int,
              b: Int)
}

Resolves rdar://problem/61461022

[nathawes]

@swift-ci please test

[AnthonyLatsis]

3 columns?

[nathawes]

12 total. Lines that aren't column aligned themselves round down to the nearest tab-width. Not sure that's the best behavior, but it's not new.

[AnthonyLatsis]

I see, thanks.