Replace QCheck unit tests with Quickcheck

[johnyob]

Dromedary's current testing framework relies on Alcotest, QCheck and Jane Street's Expect Tests.
This issue aims to remove QCheck by using Jane Street's Quickcheck library:

module T = struct
  type t = 
    | ...
  [@@deriving quickcheck]
end

let%test_unit = 
  Quickcheck.run T.quickcheck_generator ~f:(fun t -> ...)