Lazy aggregated batch verification

[dapplion]

Is your feature request related to a problem? Please describe.

Reduce load for busy gossip channels

Describe the solution you'd like

See status-im/nimbus-eth2#3212

Describe alternatives you've considered

N/A

[philknows]

As stated in the Mar 18 planning call, we should target gossipsub upgrade first, then implement this.

[wemeetagain]

@twoeths I think this is our same-message optimisation? In that case this can be closed

[twoeths]

yes but we only implemented for attestation, need to also implement for sync committee messages