beacon-chain/kv: remove pruned blocks from parent index during historical deletion#15838

Galoretka wants to merge 2 commits intoOffchainLabs:developOffchainLabs/prysm:developfrom

Galoretka:fix/db-kv-prune-parent-index-cleanupGaloretka/prysm:fix/db-kv-prune-parent-index-cleanupCopy head branch name to clipboard