Promote hashed state initially (#577)

eth/downloader/stagedsync_downloader.go

eth/downloader/stagedsync_stage_execute_test.go

eth/downloader/stagedsync_stage_hashcheck.go

eth/downloader/stagedsync_stage_hashcheck_test.go

eth/downloader/stagedsync_stage_indexes.go

eth/downloader/stagedsync_testutil.go

eth/downloader/stagedsync_utils.go

trie/flatdb_sub_trie_loader.go

trie/sub_trie_loader.go