refactor bits aggregator or operation

beacon/validator/src/main/java/tech/pegasys/teku/validator/coordinator/performance/DefaultPerformanceTracker.java

@@ -317,10 +317,7 @@ private AttestationPerformance calculateAttestationPerformance(
         slotToBitlists.merge(
             entry.getKey(),
             AttestationBitsAggregator.of(attestation, committeesSize),
-            (firstBitsAggregator, secondBitAggregator) -> {
-              firstBitsAggregator.or(secondBitAggregator);
-              return firstBitsAggregator;
-            });
+            AttestationBitsAggregator::or);
       }
     }
 

beacon/validator/src/test/java/tech/pegasys/teku/validator/coordinator/performance/DefaultPerformanceTrackerTest.java

@@ -278,8 +278,10 @@ void shouldClearOldSentObjects() {
     chainUpdater.updateBestBlock(chainUpdater.advanceChainUntil(10));
     performanceTracker.reportBlockProductionAttempt(spec.computeEpochAtSlot(UInt64.valueOf(1)));
     performanceTracker.reportBlockProductionAttempt(spec.computeEpochAtSlot(UInt64.valueOf(2)));
-    performanceTracker.saveProducedBlock(chainUpdater.chainBuilder.getBlockAtSlot(1).getSlotAndBlockRoot());
-    performanceTracker.saveProducedBlock(chainUpdater.chainBuilder.getBlockAtSlot(2).getSlotAndBlockRoot());
+    performanceTracker.saveProducedBlock(
+        chainUpdater.chainBuilder.getBlockAtSlot(1).getSlotAndBlockRoot());
+    performanceTracker.saveProducedBlock(
+        chainUpdater.chainBuilder.getBlockAtSlot(2).getSlotAndBlockRoot());
     performanceTracker.saveProducedAttestation(dataStructureUtil.randomAttestation(UInt64.ONE));
     performanceTracker.onSlot(spec.computeStartSlotAtEpoch(UInt64.valueOf(2)));
     assertThat(performanceTracker.producedAttestationsByEpoch).isEmpty();
@@ -312,8 +314,10 @@ void shouldClearObjectsAfterFailure() {
     performanceTracker.start(UInt64.ZERO);
     performanceTracker.reportBlockProductionAttempt(spec.computeEpochAtSlot(UInt64.valueOf(1)));
     performanceTracker.reportBlockProductionAttempt(spec.computeEpochAtSlot(UInt64.valueOf(2)));
-    performanceTracker.saveProducedBlock(chainUpdater.chainBuilder.getBlockAtSlot(1));
-    performanceTracker.saveProducedBlock(chainUpdater.chainBuilder.getBlockAtSlot(2));
+    performanceTracker.saveProducedBlock(
+        chainUpdater.chainBuilder.getBlockAtSlot(1).getSlotAndBlockRoot());
+    performanceTracker.saveProducedBlock(
+        chainUpdater.chainBuilder.getBlockAtSlot(2).getSlotAndBlockRoot());
     performanceTracker.saveProducedAttestation(dataStructureUtil.randomAttestation(UInt64.ZERO));
     performanceTracker.saveProducedAttestation(dataStructureUtil.randomAttestation(UInt64.ONE));
     performanceTracker.onSlot(spec.computeStartSlotAtEpoch(UInt64.valueOf(2)));

ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/attestation/utils/AttestationBitsAggregator.java

@@ -62,7 +62,7 @@ static AttestationBitsAggregator of(
         .orElseGet(() -> new AttestationBitsAggregatorPhase0(attestation.getAggregationBits()));
   }
 
-  void or(AttestationBitsAggregator other);
+  AttestationBitsAggregator or(AttestationBitsAggregator other);
 
   boolean aggregateWith(Attestation other);
 

ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/attestation/utils/AttestationBitsAggregatorElectra.java

@@ -48,8 +48,9 @@ static AttestationBitsAggregator fromAttestationSchema(
   }
 
   @Override
-  public void or(final AttestationBitsAggregator other) {
+  public AttestationBitsAggregator or(final AttestationBitsAggregator other) {
     or(other.getCommitteeBits(), other.getAggregationBits(), false);
+    return this;
   }
 
   @Override

ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/attestation/utils/AttestationBitsAggregatorPhase0.java

@@ -33,8 +33,9 @@ static AttestationBitsAggregator fromAttestationSchema(
   }
 
   @Override
-  public void or(final AttestationBitsAggregator other) {
+  public AttestationBitsAggregator or(final AttestationBitsAggregator other) {
     aggregationBits = aggregationBits.or(other.getAggregationBits());
+    return this;
   }
 
   @Override