Refactor celestia-node usage

[evan-forbes]

Currently, we are downloading the entire block to create the DataAvailabilityHeader in order to DAS. This obviously defeats the purpose of DAS, and was added a few months ago before celestia-node had implemented the ability to gossip headers. We want to change that, and actually use celestia-node properly.

• Stop downloading the entire block to create the DAH
• Use celestia-node to gossip headers, DAS properly, retrieve optimint blocks properly