Redeemer format is wrong when marshaling to CBOR

[agaffney]

We're generating this:

            5: {
                "Redeemers": {
                    [0, 1]: [{}, [77308_2, 23525984_2]],
                    [0, 2]: [{}, [25305_1, 8177555_2]],
                    [3, 0]: [{}, [1315966_2, 424372602_2]],
                },
            },

when we want:

            5: [
                [0, 2, 121_0([]), [25305_1, 8177555_2]],
                [0, 1, 121_0([]), [77308_2, 23525984_2]],
                [
                    3,
                    0,
                    121_0([_
                        0,
                        [_ 700000_2],
                        h'00',
                        122_0([]),
                        [_ 122_0([])],
                    ]),
                    [1315966_2, 424372602_2],
                ],
            ],

We are also adding an "empty" redeemer to the output when none is defined:

            5: {"Redeemers": null},