eds: Store.CARBlockstore

[Wondertan]

CARBlockstore method returns a [Blockstore][blockstore] interface implementation instance, providing random access
over share and NMT Merkle proof in a specific EDS identified by DataHash. It is required for FNs/BNs to enable reading
data by namespace.

NOTES:

• The Blockstore does not store whole Celestia Blocks, but IPFS blocks. We represent Merkle proofs and shares in IPFS
  blocks.

// CARBlockstore returns an IPFS Blockstore providing access to individual shares/nodes of a specific EDS identified by 
// DataHash and 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) CARBlockstore(DataHash) (blockstore.Blockstore, error)

[distractedm1nd]

Closed with #1395 , must have not linked correctly.