Slasher: False negative for surrounded votes

[nalepae]

Describe the bug

processQueuedAttestations it the following:

func (s *Service) processQueuedAttestations(ctx context.Context, slotTicker <-chan primitives.Slot) {
	defer s.wg.Done()

	for {
		select {
		case currentSlot := <-slotTicker:
			attestations := s.attsQueue.dequeue()
			currentEpoch := slots.ToEpoch(currentSlot)
   ...

If:

• when we enter a first time in the case currentSlot := <-slotTicker, the queue contain an attestation A, and if,
• when we enter a second time in case currentSlot := <-slotTicker, the queue contain an attestation B, and if,
• B is surrounded by A

then no slashing offense will be detected ==> ❌

Additional notes:

If:

• when we enter a first time in the case currentSlot := <-slotTicker, the queue contain two attestations A and B and if,
• B is surrounded by A, or if
• B surrounds by A

then the slashing offence will be detected. ==> ✅

If:

• when we enter a first time in the case currentSlot := <-slotTicker, the queue contain an attestation A, and if,
• when we enter a second time in case currentSlot := <-slotTicker, the queue contain an attestation B, and if,
• B surrounds A

then the slashing offence will be detected. ==> ✅

Has this worked before in a previous version?

Probably not.