Print nested lambdas with a single lambda expression
The parser desugars lambdas with multiple arguments, like
const = \a _ -> a, into nested lambdas, like
const = \a -> \_ -> a. As seen in #30 (closed) , currently we output the latter, but it seems like in most cases people will prefer the former, and we should try to default to printing it that way.
Alternatively, we might be able to make another compiler PR to preserve this metadata, but I'm less sure that it's worth it here than for where-bindings.