[Merged by Bors] - add ssz support in request body for /beacon/blocks endpoints (v1 & v2)#4479

eserilev wants to merge 10 commits intosigp:unstablesigp/lighthouse:unstablefrom

eserilev:support-ssz-for-post-beacon-blockeserilev/lighthouse:support-ssz-for-post-beacon-blockCopy head branch name to clipboard