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/tributary/src/tendermint.rs

@@ -125,7 +125,7 @@ pub(crate) struct Validators {
 impl Validators {
   pub(crate) fn new(
     genesis: [u8; 32],
-    validators: HashMap<<Ristretto as Ciphersuite>::G, u64>,
+    validators: Vec<(<Ristretto as Ciphersuite>::G, u64)>,
   ) -> Option<Validators> {
     let mut total_weight = 0;
     let mut weights = HashMap::new();