This pull request fixes a flaw in prefetcher.
In verkle tree world, both accounts and storage slots are committed into
a single tree instance for state hashing. If the prefetcher is activated, we will
try to pull the trie for the prefetcher for performance speedup.
However, we had a special logic to skip pulling storage trie if the
storage root is empty. While it's true for merkle as we have nothing to
do with an empty storage trie, it's totally wrong for verkle. The consequences
for skipping pulling is the storage changes are committed into trie A, while the
account changes are committed into trie B (pulled from the prefetcher), boom.
922eb033d3