Genesis sync from existing snapshots (#3087)

cmd/hack/hack.go

cmd/integration/commands/snapshot_check.go

cmd/integration/commands/stages.go

cmd/integration/commands/state_stages.go

cmd/rpcdaemon/README.md

cmd/rpcdaemon/cli/config.go

cmd/rpcdaemon/interfaces/interfaces.go

cmd/state/commands/regenerate_txlookup.go

cmd/state/generate/regenerate_tx_lookup.go

cmd/utils/flags.go

common/hasher.go

consensus/clique/clique.go

core/rawdb/accessors_chain.go

eth/backend.go

eth/ethconfig/config.go

eth/stagedsync/stage_blockhashes.go

eth/stagedsync/stage_bodies.go

eth/stagedsync/stage_execute.go

eth/stagedsync/stage_headers.go

eth/stagedsync/stage_senders.go