Add a test to the coordinator for running a Tributary

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.

coordinator/Cargo.toml

@@ -26,6 +26,8 @@ frost = { package = "modular-frost", path = "../crypto/frost" }
 
 scale = { package = "parity-scale-codec", version = "3", features = ["derive"] }
 
+sp-application-crypto = { git = "https://github.com/serai-dex/substrate", default-features = false }
+
 serai-db = { path = "../common/db" }
 
 processor-messages = { package = "processor-messages", path = "../processor/messages" }