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/src/tributary/mod.rs

@@ -91,12 +91,8 @@ impl TributarySpec {
     None
   }
 
-  pub fn validators(&self) -> HashMap<<Ristretto as Ciphersuite>::G, u64> {
-    let mut res = HashMap::new();
-    for (key, amount) in self.validators.clone() {
-      res.insert(key, amount);
-    }
-    res
+  pub fn validators(&self) -> Vec<(<Ristretto as Ciphersuite>::G, u64)> {
+    self.validators.clone()
   }
 }