In the initialization procedure for pallet-babe, we compute randomness using make_bytes for primary slots and assign an Initialized value based on that.

Secondary-VRF slot assignments also provide some randomness that we should assign to an ephemeral storage value that other modules can access. It shouldn't go in the Initialized value because that is used for the epoch randomness calculation, which shouldn't be polluted by secondary slots.

Implementation:

Add a separate storage var AuthorVrfRandomness which is filled either by Primary or SecondaryVRF slot claims. Add a getter author_vrf_randomness.