share: EDSStore.Blockstore

[Wondertan]

Context

Blockstore method returns a Blockstore interface implementation instance, providing random access over share and NMT Merkle proof in every stored EDS. It is required for FNs/BNs to serve DAS requests over the Bitswap and for reading data by namespace.

Implementation Details

There is a frozen/un-merged implementation of Blockstore over DAGStore and CARv2 indexes. EDIT: Already unfrozen and almost ready to be merged

NOTES:

• We can either use it(and finish if something is missing for our case) or implement custom optimized for our needs(feat(blocksync): WIP experiments with DAGStore as a Blockstore #1051)
• The Blockstore does not store whole Celestia Blocks, but IPFS blocks. We represent Merkle proofs and shares in IPFS
  blocks.

// Blockstore returns an IPFS Blockstore providing access to individual shares/nodes of all EDS 
// registered on the Store. NOTE: The Blockstore does not store whole Celestia Blocks but IPFS blocks. 
// We represent `shares` and NMT Merkle proofs as IPFS blocks and IPLD nodes so Bitswap can access those.
func (s *Store) Blockstore() blockstore.Blockstore