Adds snap/2 (EIP-8189), a block-access-list (BAL) based state sync, and
wires it to run side by side with snap/1. It's opt-in (for now) behind a
new --snap.v2 flag and chosen at startup.
https://eips.ethereum.org/EIPS/eip-8189
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Co-authored-by: Toni Wahrstätter <info@toniwahrstaetter.com>
Co-authored-by: Gary Rong <garyrong0905@gmail.com>
