chore: update skyway validator nonces (#1288)

# Related Github tickets

- VolumeFi#2159

# Background

When a claim is set to observed, update all validator nonces if they
have a lower last observed nonce.

NOTE: This only takes effect when a claim is successfully attested to.
The validators currently stuck will remain on their current nonces until
a claim is processed. To get them unstuck, we need
VolumeFi#2160

# Testing completed

- [ ] test coverage exists or has been added/updated
- [x] tested in a private testnet

# Breaking changes

- [x] I have checked my code for breaking changes
- [x] If there are breaking changes, there is a supporting migration.

x/skyway/keeper/attestation.go

@@ -164,6 +164,13 @@ func (k Keeper) TryAttestation(ctx context.Context, att *types.Attestation) erro
 					return err
 				}
 
+				// Update all validator nonces to the claim nonce that was just
+				// processed
+				err = k.updateValidatorNoncesIfHigher(ctx, claim.GetChainReferenceId(), claim.GetSkywayNonce())
+				if err != nil {
+					return err
+				}
+
 				break
 			}
 		}

x/skyway/keeper/keeper.go

@@ -480,3 +480,31 @@ func (k Keeper) overrideNonce(ctx context.Context, chainReferenceId string, nonc
 	logger.Info("Updated last observed nonce successfully")
 	return nil
 }
+
+// updateValidatorNoncesIfHigher updates all validator nonces to `newNonce` only
+// if it is higher than the current record
+func (k Keeper) updateValidatorNoncesIfHigher(
+	ctx context.Context,
+	chainReferenceId string,
+	newNonce uint64,
+) error {
+	logger := liblog.FromKeeper(ctx, k).WithComponent("update-validator-nonces-if-higher")
+
+	store := k.GetStore(ctx, chainReferenceId)
+	prefixStore := prefix.NewStore(store, types.LastEventNonceByValidatorKey)
+
+	err := k.IterateValidatorLastEventNonces(ctx, chainReferenceId, func(key []byte, nonce uint64) bool {
+		if newNonce > nonce {
+			prefixStore.Set(key, types.UInt64Bytes(newNonce))
+		}
+
+		return false
+	})
+	if err != nil {
+		logger.WithError(err).Warn("Failed to update validator skyway nonces")
+		return err
+	}
+
+	logger.Info("Updated validator nonces to highest successfully")
+	return nil
+}