Update attestation related APIs to be compatible with EIP-7549

[tbenr]

attestations for Electra require an additional committee_bits field.

I think these APIs are effected.
/eth/v1/beacon/pool/attestations
/eth/v1/beacon/blocks/{block_id}/attestations
/eth/v1/validator/aggregate_attestation

[rkapka]

Also /eth/v1/validator/aggregate_and_proofs

[ensi321]

Something minor but I believe attester slashing is affected because the max length of attesting_indices in IndexedAttestation is changed.
So get and post /eth/v1/beacon/pool/attester_slashings

[tersec]

Would note that there's a conceptual difference in get/put type APIs. Both worth discussing, but adding polymorphism present challenges to different parts of the stack. The initial list of three all returns an Attestation-like structure for example, which implies a particular type system setup to handle that.

[tersec]

https://ethereum.github.io/beacon-APIs/#/Events/eventstream has an attestation event type, potentially affected

[tbenr]

I suspect we need to move /eth/v1/validator/aggregate_attestation to v2, 'cose committee index parameter is required to BN if we want to produce aggregates only for the committee the validator is in.
cc @mkalinin

[mkalinin]

I suspect we need to move /eth/v1/validator/aggregate_attestation to v2, 'cose committee index parameter is required to BN if we want to produce aggregates only for the committee the validator is in. cc @mkalinin

Yes, the committee_index has to be passed explicitly onto this call, because the EIP tends to preserve the network part of the aggregation strategy