Most of coordinator Tributary retiry

Adds Event::SetRetired to validator-sets.

Emit TributaryRetired.

Replaces is_active_set, which made multiple network requests, with
is_retired_tributary, a DB read.

Performs most of the removals necessary upon TributaryRetired.

Still needs to clean up the actual Tributary/Tendermint tasks.

substrate/client/src/serai/validator_sets.rs

@@ -33,6 +33,13 @@ impl<'a> SeraiValidatorSets<'a> {
       .await
   }
 
+  pub async fn set_retired_events(&self) -> Result<Vec<ValidatorSetsEvent>, SeraiError> {
+    self
+      .0
+      .events::<ValidatorSets, _>(|event| matches!(event, ValidatorSetsEvent::SetRetired { .. }))
+      .await
+  }
+
   pub async fn session(&self, network: NetworkId) -> Result<Option<Session>, SeraiError> {
     self.0.storage(PALLET, "CurrentSession", Some(vec![scale_value(network)])).await
   }

substrate/in-instructions/pallet/src/lib.rs

@@ -174,7 +174,10 @@ pub mod pallet {
       // key is publishing `Batch`s. This should only happen once the current key has verified all
       // `Batch`s published by the prior key, meaning they are accepting the hand-over.
       if prior.is_some() && (!valid_by_prior) {
-        ValidatorSets::<T>::retire_session(network, Session(current_session.0 - 1));
+        ValidatorSets::<T>::retire_set(ValidatorSet {
+          network,
+          session: Session(current_session.0 - 1),
+        });
       }
 
       // check that this validator set isn't publishing a batch more than once per block

substrate/staking/pallet/src/lib.rs

@@ -13,7 +13,10 @@ pub mod pallet {
 
   use serai_primitives::{NetworkId, Amount, PublicKey};
 
-  use validator_sets_pallet::{primitives::Session, Config as VsConfig, Pallet as VsPallet};
+  use validator_sets_pallet::{
+    primitives::{Session, ValidatorSet},
+    Config as VsConfig, Pallet as VsPallet,
+  };
   use pallet_session::{Config as SessionConfig, SessionManager};
 
   #[pallet::error]
@@ -183,7 +186,12 @@ pub mod pallet {
       Some(VsPallet::<T>::select_validators(NetworkId::Serai))
     }
 
-    fn end_session(_end_index: u32) {}
+    fn end_session(end_index: u32) {
+      VsPallet::<T>::retire_set(ValidatorSet {
+        network: NetworkId::Serai,
+        session: Session(end_index),
+      })
+    }
 
     fn start_session(_start_index: u32) {}
   }

substrate/validator-sets/pallet/src/lib.rs

@@ -235,6 +235,7 @@ pub mod pallet {
   pub enum Event<T: Config> {
     NewSet { set: ValidatorSet },
     KeyGen { set: ValidatorSet, key_pair: KeyPair },
+    SetRetired { set: ValidatorSet },
   }
 
   impl<T: Config> Pallet<T> {
@@ -592,10 +593,10 @@ pub mod pallet {
       Self::participants(network).into()
     }
 
-    pub fn retire_session(network: NetworkId, session: Session) {
-      let set = ValidatorSet { network, session };
+    pub fn retire_set(set: ValidatorSet) {
       MuSigKeys::<T>::remove(set);
       Keys::<T>::remove(set);
+      Pallet::<T>::deposit_event(Event::SetRetired { set });
     }
 
     /// Take the amount deallocatable.