* Simplify block quarantine blobless
The quarantine blobless table was initially keyed off of (Eth2Digest,
ValidatorSig). This was modelled off the orphan table. The presence of
the signature in the key is necessary for orphans, because we can't
verify the signature for an orphan. That is not the case for a
blobless block, where the signature can be verified.
So this PR changes the blobless block table to be keyed off a
Eth2Digest only. This simplifies the retrieval and handling of
blobless blocks.
* review feedback
29b431e312