core/rawdb, core/state/snapshot: runtime snapshot generation

cmd/geth/main.go

cmd/geth/usage.go

cmd/utils/flags.go

core/blockchain.go

core/rawdb/database.go

core/rawdb/schema.go

core/state/snapshot/difflayer.go

core/state/snapshot/difflayer_test.go

core/state/snapshot/disklayer.go

core/state/snapshot/disklayer_test.go

core/state/snapshot/generate.go

core/state/snapshot/journal.go

core/state/snapshot/snapshot.go

core/state/snapshot/snapshot_test.go

core/state/snapshot/wipe.go

core/state/snapshot/wipe_test.go

core/state/statedb.go

eth/backend.go

eth/config.go

trie/iterator.go