Implement BlobPool.ContentFrom which was previously stubbed to return
empty results. The method now returns blob transactions for a given
address with blob sidecars stripped to avoid excessive data transfer.
Blob versioned hashes remain available on the returned transactions.
Pending transactions are resolved from the on-disk store via the
in-memory index, while gapped (queued) transactions are returned
from the in-memory reorder buffer. The per-account bound of 16
transactions (maxTxsPerAccount) keeps the disk read cost trivial,
unlike Content() which would need to load all accounts.
Fixes#31977
