chore(compiler)!: Disallow end-of-line before =>

[phated]

This removes support for newlines before =>. This came up while I was trying to work on #1113 with @ospencer. We don't allow newlines before ->, so menhir got really mad when I switched them to => and Oscar said it would be really hard to resolve.

I started typing out examples of eol before arrow and they looked really terrible:

let a =
  () => 1

match (a) {
    x
      => 2
}

It seems easiest to just remove support for eol before an arrow. I hope y'all agree.

(Is it a chore? Who knows 🤷 )

[phated]

I need @ospencer to look at the messages file because I updated it and it seems that it might have been out-of-date from other changes, because it changed a ton.

[ospencer]

There's a couple of minor things that changed, but no big deal. It's only comments, so there's nothing to worry about. Pretty much any change to the parser will renumber many of the states.

[marcusroberts]

Looks good!