Support blobSidecars lookup API by versionedHashes

[tbenr]

There is interest from L2s (Linea in particular) to support this way of querying the blobs.

ethereum/beacon-APIs#332 (comment)

It will be a feature flag, default disabled, because we will need to maintain an index in DB
(ie versionedHash->slotAndBlockRootAndBlobIndex) because we don't currently store versionedHashes anywhere.

so when enabling the feature (ie --Xstore-blob-versioned-hashes-enabled) it will start feeding the db index so when the optional parameter versioned_hashes is used. Note that using that will make the block_id not required anymore.
In that mode versioned_hashes list will be the only param.