Add record declaration syntax

[janmasrovira]

• Closes Add record declaration syntax support  #1641

This pr adds the option to declare constructors with fields. E.g.

type Pair (A B : Type) :=
  | mkPair {
      fst : A;
      snd : B
    };

Which is desugared to

type Pair (A B : Type) :=
  | mkPair :  (fst : A) -> (snd : B) -> Pair A B;

making it possible to write mkPair (fst := 1; snd := 2).

Mutli-constructor types are also allowed to have fields.