TendermintMachine may equivocate on reboot

[kayabaNerve]

One method would be to wait till the next block after boot, to ensure it doesn't, yet then it risks stalling if every node goes offline (as on reboot, they'll all wait for the next block which will never come).

[kayabaNerve]

#561 will fix this.

[kayabaNerve]

This was solved in the cited PR:

serai/coordinator/tributary/tendermint/src/block.rs

Lines 189 to 203 in 875c669

	// Check we haven't sent this message within this round
	let msg_key = key(match res.data.step() {
	Step::Propose => PROPOSE_KEY,
	Step::Prevote => PEVOTE_KEY,
	Step::Precommit => PRECOMMIT_KEY,
	});
	if txn.get(&msg_key).is_some() {
	assert!(!new_block);
	assert!(!new_round);
	None?;
	}
	// Put that we're sending this message to the DB
	txn.put(&msg_key, []);
	txn.commit();