fix: cache attester index during attestation validation

[nflaig]

Motivation

Currently we always try to get the validator index from attestationOrCache.attestation but it might be null if cached value is used leading to the following error:

Nov-28 13:33:21.898[network]         debug: Gossip batch validation beacon_attestation threw a non-AttestationError - Cannot read properties of null (reading 'attesterIndex')
TypeError: Cannot read properties of null (reading 'attesterIndex')
    at validateAttestationNoSignatureCheck (file:///usr/app/packages/beacon-node/src/chain/validation/attestation.ts:426:93)
    at validateGossipAttestationsSameAttData (file:///usr/app/packages/beacon-node/src/chain/validation/attestation.ts:119:43)
    at Object.beacon_attestation (file:///usr/app/packages/beacon-node/src/network/processor/gossipHandlers.ts:625:64)
    at NetworkProcessor.gossipValidatorBatchFn (file:///usr/app/packages/beacon-node/src/network/processor/gossipValidatorFn.ts:36:75)
    at NetworkProcessor.processPendingGossipsubMessage (file:///usr/app/packages/beacon-node/src/network/processor/index.ts:438:20)
    at NetworkProcessor.executeWork (file:///usr/app/packages/beacon-node/src/network/processor/index.ts:398:16)
    at NetworkProcessor.pushPendingGossipsubMessageToQueue (file:///usr/app/packages/beacon-node/src/network/processor/index.ts:310:10)
    at NetworkProcessor.onPendingGossipsubMessage (file:///usr/app/packages/beacon-node/src/network/processor/index.ts:298:10)
    at NetworkEventBus.emit (node:events:520:28)

Caching the attester index also has some benefits pre-electra as we can safe a getSingleTrueBit call (see #7209) if we retrieve the attestation from the cache.

Description

Cache attester index during attestation validation

[nflaig]

@twoeths I am not sure about this comment, seems simpler to keep the committee index in the cache as if in case of loading the attestation from cache we won't deserialize the SingleAttestation to get the committe index from there, and for pre-electra we would still need it.

[twoeths]

yes let's keep it in the cache and remove "TODO"

[nflaig]

could consider renaming validatorIndex to attesterIndex (or vice versa)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 11 lines in your changes missing coverage. Please review.

Project coverage is 48.43%. Comparing base (cfe6c89) to head (59b3b1e).

Additional details and impacted files

@@             Coverage Diff              @@
##           devnet-5    #7260      +/-   ##
============================================
- Coverage     48.44%   48.43%   -0.01%     
============================================
  Files           602      602              
  Lines         40321    40328       +7     
  Branches       2057     2057              
============================================
  Hits          19532    19532              
- Misses        20751    20758       +7     
  Partials         38       38              

[twoeths]

it's not correct to have attesterIndex here, this is the common cache for the whole committee while this is specific information of a validator

should also remove aggregationBits below as it's specific to the validator

[nflaig]

Closing as we need a different approach