Research Bitswap extension to avoid the top-level index in share.EDStore

[Wondertan]

Context

Based on #1099, disk usage will increase from the top-level index. This is a temporary solution and the index will have to be removed. LNs know which block they sample and can provide DataRoot's hash together with sample request over Bitswap, removing the need for hash-to-eds-file mapping. This requires us to either facilitate the implementation of Bitswap's auth extension or propose a custom Bitswap message extension. Subsequently, the Blockstore implementation provided via EDSStore would have to be changed to expect DataRoot's hash to be passed through thecontext.Context.

[Wondertan]

We found a way by using custom multihash which is now implemented in #2675