We had a race condition where'd we be informed of blocks 1 .. 3, and
immediately add 1 .. 3. Because we immediately tried to add 2 after 1, it'd
fail since the tip was still the genesis, yet 2 needs the tip to be 1.
Adding a channel, while ugly, was the simplest way to accomplish this.
Also has any added block be broadcasted. Else there's a race condition where a
node which syncs up to the most recent block does so, yet fails to add the next
block when it's committed to.
This defines the tart of a very complex series of locks I'm really unhappy
with. At the same time, there's not immediately a better solution. This also
should work without issue.
Impls a LocalP2p for testing.
Moves rebroadcasting into Tendermint, since it's what knows if a message is
fully valid + original.
Removes TributarySpec::validators() HashMap, as its non-determinism caused
different instances to have different round robin schedules. It was already
prior moved to a Vec for this issue, so I'm unsure why this remnant existed.
Also renames the GH no-std workflow from the prior commit.
