PFG: multi-collator support with monotonic drand #392
Description
Currently, we do no guarantee that we ingest an unbroken sequence of drand pulses, only that we produce newer ones. In order to support tlock, we need to ensure we can ingest any given pulse. To do so, we need to implement a gossip layer between authorities participating in the PFG in order to gossip their latest finalized round to other collators.
In the current impl, they read the maximum number of pulses allowed from their queue (at most 6 right now, normally they only have 2, sometimes 1). It attempts to ingest an unbroken sequence, but cannot guarantee or enforce it.
In addition to these, we need to update how the gadget ingests pulses. Now, it jsut takes the latest single pulse it has and injects it to ensure that older pulses are always ignored, however, we eventually want to guarantee that all pulses are handled.