move staged sync to tx (#1897)

cmd/headers/download/downloader.go

cmd/integration/commands/snapshot_check.go

cmd/integration/commands/stages.go

cmd/integration/commands/state_stages.go

cmd/tgcustom/main.go

eth/backend.go

eth/downloader/downloader.go

eth/downloader/downloader_stagedsync.go

eth/stagedsync/all_stages.go

eth/stagedsync/replacement_stages.go

eth/stagedsync/stage.go

eth/stagedsync/stage_blockhashes.go

eth/stagedsync/stage_blockhashes_test.go

eth/stagedsync/stage_bodies_snapshot.go

eth/stagedsync/stage_finish.go

eth/stagedsync/stage_headers_new.go

eth/stagedsync/stage_headers_snapshot.go

eth/stagedsync/stage_interhashes.go

eth/stagedsync/stage_state_snapshot.go

eth/stagedsync/stagebuilder.go