Confusing parser error messages on wrong kind

[jiribenes]

There are a lot of confusing error messages from the parser when writing things like:

record Fun(f: (Int, Int) => Bool)
//                       ^^
// Expected ) but got =>

def foo { f: (Int, Int) => Bool at {} } = <>
//                         ^^^^
// Expected an interface type.

def bar(f: (Int, Int) => Bool) = <>
//                    ^^
// Expected ) but got =>

They all stem from the fact that we distinguish between computation types and value types in the parser.
Instead, we should parse some generic, kind-less type and only resolve it properly some time later (ideally in Typer?)

My preferred error messages would be something like:

record Fun(f: (Int, Int) => Bool)
//            ~~~~~~~~~~~~~~~~~~
//
// Expected a value type, got a computation type.
// Did you mean: `(Int, Int) => Bool at {}`?

def foo { f: (Int, Int) => Bool at {} } = <>
//            ~~~~~~~~~~~~~~~~~~~~~~~
//
// Expected a computation type, got a value type.
// Did you mean:
// 1. `{ f: (Int, Int) => Bool }`?
// 2. `(f: (Int, Int) => Bool at {})`?

def bar(f: (Int, Int) => Bool) = <>