Gloas PayloadAttestation gossip verification (#9145)

Co-Authored-By: hopinheimer <knmanas6@gmail.com>

Co-Authored-By: hopinheimer <48147533+hopinheimer@users.noreply.github.com>

Co-Authored-By: Eitan Seri-Levi <eserilev@ucsc.edu>

Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

beacon_node/beacon_chain/src/observed_attesters.rs

@@ -42,6 +42,8 @@ pub type ObservedSyncContributors<E> =
 pub type ObservedAggregators<E> = AutoPruningEpochContainer<EpochHashSet, E>;
 pub type ObservedSyncAggregators<E> =
     AutoPruningSlotContainer<SlotSubcommitteeIndex, (), SyncAggregatorSlotHashSet, E>;
+pub type ObservedPayloadAttesters<E> =
+    AutoPruningSlotContainer<Slot, (), PayloadAttesterSlotHashSet<E>, E>;
 
 #[derive(Debug, PartialEq)]
 pub enum Error {
@@ -255,6 +257,46 @@ impl Item<()> for SyncAggregatorSlotHashSet {
     }
 }
 
+/// Stores a `HashSet` of validator indices that have sent a payload attestation gossip
+/// message during a slot.
+pub struct PayloadAttesterSlotHashSet<E> {
+    set: HashSet<usize>,
+    phantom: PhantomData<E>,
+}
+
+impl<E: EthSpec> Item<()> for PayloadAttesterSlotHashSet<E> {
+    fn with_capacity(capacity: usize) -> Self {
+        Self {
+            set: HashSet::with_capacity(capacity),
+            phantom: PhantomData,
+        }
+    }
+
+    /// Defaults to `PTC_SIZE`, the maximum number of payload attesters per slot.
+    fn default_capacity() -> usize {
+        E::ptc_size()
+    }
+
+    fn len(&self) -> usize {
+        self.set.len()
+    }
+
+    fn validator_count(&self) -> usize {
+        self.set.len()
+    }
+
+    /// Inserts the `validator_index` in the set. Returns `true` if the `validator_index` was
+    /// already in the set.
+    fn insert(&mut self, validator_index: usize, _value: ()) -> bool {
+        !self.set.insert(validator_index)
+    }
+
+    /// Returns `true` if the `validator_index` is in the set.
+    fn get(&self, validator_index: usize) -> Option<()> {
+        self.set.contains(&validator_index).then_some(())
+    }
+}
+
 /// A container that stores some number of `T` items.
 ///
 /// This container is "auto-pruning" since it gets an idea of the current slot by which