Log the signed head in sync message submission #4247
Description
🎯 Problem to be solved
Given that VCs use different mechanisms to acquire the head to be signed for the sync message, we cannot deterministically choose an endpoint to gatekeep with a QBFT consensus between the nodes.
As a first step it would be nice to at least track who is providing signature of what - log the beacon_block_root Charon received for each sync_message partial signature.