Stop validators from equivocating on reboot

Part of https://github.com/serai-dex/serai/issues/345.

The lack of full DB persistence does mean enough nodes rebooting at the same
time may cause a halt. This will prevent slashes.

coordinator/tributary/tendermint/src/ext.rs

@@ -212,6 +212,9 @@ pub trait Block: Send + Sync + Clone + PartialEq + Eq + Debug + Encode + Decode
 /// Trait representing the distributed system Tendermint is providing consensus over.
 #[async_trait]
 pub trait Network: Sized + Send + Sync {
+  /// The database used to back this.
+  type Db: serai_db::Db;
+
   // Type used to identify validators.
   type ValidatorId: ValidatorId;
   /// Signature scheme used by validators.