The PFG is run by every collator currently. This causes there to be a lot of wasted work on the network. Instead, like Aura, we can use a round-robin authority selection mechanism. This would be first checked in the worker where we actually build the extrinsic, then verified when we call try_submit_asig in the RandomnessBeaconPallet. In this initial version, we lay the groundwork for this but note that this is a single-authority protocol at the moment.

In addition, the collator should still send an unsigned tx but with a signed payload. We then use this signature to verify that the caller is the expected authority.