Add Erigon Import feature for Hive integration purpose (#3298)

cmd/erigon/main.go

cmd/erigoncustom/main.go

cmd/utils/flags.go

eth/backend.go

eth/ethconfig/config.go

turbo/app/import.go

turbo/app/init.go

turbo/app/make_app.go

turbo/app/snapshots.go

turbo/stages/bodydownload/prefetched_blocks.go

turbo/stages/headerdownload/header_algos.go

turbo/stages/stageloop.go