* Rewrite tendermint's message handling loop to much more clearly match the paper
No longer checks relevant branches upon messages, yet all branches upon any
state change. This is slower, yet easier to review and likely without one or
two rare edge cases.
When reviewing, please see page 5 of https://arxiv.org/pdf/1807.04938.pdf.
Lines from the specified algorithm can be found in the code by searching for
"// L".
* Sane rebroadcasting of consensus messages
Instead of broadcasting the last n messages on the Tributary side of things, we
now have the machine rebroadcast the message tape for the current block.
* Only rebroadcast messages which didn't error in some way
* Only rebroadcast our own messages for tendermint
Instead of saving, for every sent message, if it was sent or not, we track the
latest block/round participated in. These two keys are comprehensive to all
prior block/rounds. We then use three keys for the latest round's
proposal/prevote/precommit, enabling tracking current state as necessary to
prevent equivocations with just 5 keys.
The storage of the latest three messages also enables proper rebroadcasting of
the current round (not implemented in this commit).
Part of https://github.com/serai-dex/serai/issues/345.
The lack of full DB persistence does mean enough nodes rebooting at the same
time may cause a halt. This will prevent slashes.
