Bridge Node Arch - Further syncing steps

[Wondertan]

Right now BN gets block data and block header by listening for events from Core's RPC. Soon, there will be a new event and endpoint there that will allow us to get the data in one request or recent block event(celestiaorg/celestia-core#940). This PR made me think about possible paths we can leverage this feature for our BN.

• Revive an old idea about making DASer available on the BN by implementing CoreAvailbility or CoreGetter. That is, CoreListener notifies us about a new header, which eventually lands on DASer, which goes to the core component that requests data from the Core by its Root.
  • Simplifies and unifies BN data syncing maintainability because it became the same as for FN/LN
  • Removes obscure data storing logic in core
  • Requires changing the app's PR to decouple data and header events and endpoints.
• Instead, make a share.Putter putter API in the share domain that allows putting EDS data into the cel-node. Also, the header broadcasting API on the header domain. The core domain would then listen for the SignedBlock/Data events from the core and use both of the APIs to add two types of data explicitly
  • Also, it does not require any changes to the app's PR
  • Also, removes obscure data storing logic in core
  • Enables top-level API to actually write data to cel-node and not only ready.

Personally, I like both approaches, but more inclined toward the second.