Scala: model partial functions with short match syntax

[greg-at-moderne]

What's changed?

Fixing how Scala partial function literals with short match syntax are parsed, e.g.

                val f: Int => Int = {
                  case 1 => 1
                }

Squeezing them into a J.Lambda, but with a marker to denote the short syntax is used.

What's your motivation?

Currently it fails idempotency expectation.