Review uncurried error messages.

[cristianoc]

After changing to the new representation of uncurried functions (#5870) there are a few places in the codebase that used to generate error messages for which there were no tests:

• 1 fprintf ppf "This function has uncurried type, it needs to be applied in ucurried style" in Typecore. Same as 3, and overridden in Super_typecore.
• 2 fprintf ppf "This expression is excpeted to have an uncurried function" in Typecore. Same as 4 but misspelled and overridden in Super_typecore.
• 3 This is an uncurried ReScript function. @{<info>It must be applied with a dot@}.@ in Super_typecore Remove errors for curried application of uncurried functions. #5890

let foo = (. x, y) => x+1
let z = foo( 1)

• 4 fprintf ppf "This expression is expected to have an uncurried function" in Super_typecore Restore error where uncurried type is expected. #5891

let apply = (f) => f(. 1)
let z = apply(x => x+1)

• 5 The internal representation of uncurried types can escape Uncurried internal representation escapes in error message. #5892

let nonfun = 2
let _ = nonfun(. 3)

Old error:

This has type: int
  Somewhere wanted: Js.Fn.arity1<'a>

New error:

 This has type: int
  Somewhere wanted: \"function$"<'a, [#Has_arity1]>