Transition period from 4844-style blob transactions to PeerDAS-style blob transactions

[ralexstokes]

this repo is not the most appropriate place for this topic, so if you see a better one, please suggest and we can move

we want to make sure that EL clients handle the blob format transition well

around the fork boundary, we can see different types of blob messages and client gossip should be tolerant to both

leaving this here as a tracking issue for now

also cc @fradamt who has some more ideas around specific methods to handle

[ralexstokes]

update: on ethereum/pm#1415 we decided to iron out exact details here later on (e.g. peerdas-devnet-6 or later)