cmd, core, eth: background transaction indexing (#20302)

* 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>

cmd/geth/usage.go

@@ -78,6 +78,7 @@ var AppHelpFlagGroups = []flagGroup{
 			utils.SyncModeFlag,
 			utils.ExitWhenSyncedFlag,
 			utils.GCModeFlag,
+			utils.TxLookupLimitFlag,
 			utils.EthStatsURLFlag,
 			utils.IdentityFlag,
 			utils.LightKDFFlag,