* cmd, core, eth: init tx lookup in background

* core/rawdb: tiny log fixes to make it clearer what's happening

* core, eth: fix rebase errors

* core/rawdb: make reindexing less generic, but more optimal

* rlp: implement rlp list iterator

* core/rawdb: new implementation of tx indexing/unindex using generic tx iterator and hashing rlp-data

* core/rawdb, cmd/utils: fix review concerns

* cmd/utils: fix merge issue

* core/rawdb: add some log formatting polishes

Co-authored-by: rjl493456442 <garyrong0905@gmail.com>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>
# Conflicts:
#	accounts/abi/bind/backends/simulated.go
#	cmd/geth/main.go
#	cmd/geth/usage.go
#	cmd/utils/flags.go
#	consensus/clique/snapshot_test.go
#	core/bench_test.go
#	core/block_validator_test.go
#	core/blockchain.go
#	core/blockchain_test.go
#	core/chain_makers_test.go
#	core/dao_test.go
#	core/rawdb/accessors_indexes.go
#	core/rawdb/schema.go
#	eth/config.go
#	eth/helper_test.go
#	eth/sync.go
#	light/odr_test.go
#	light/trie_test.go
#	light/txpool_test.go
#	miner/worker_test.go
#	tests/block_test_util.go