cmd: allow file descriptor limit to be set via CLI (#24477)

* eth, cmd: allow FdLimit to be set in config/command line (#24148)

* eth/ethconfig: format code

* cmd, eth/ethconfig: simplify fdlimit arg, disallow toml

* cnd/utils: make fdlimit setting nicer on the logs

Co-authored-by: Gary Rong <garyrong0905@gmail.com>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>

cmd/geth/main.go

@@ -118,6 +118,7 @@ var (
 		utils.CacheSnapshotFlag,
 		utils.CacheNoPrefetchFlag,
 		utils.CachePreimagesFlag,
+		utils.FDLimitFlag,
 		utils.ListenPortFlag,
 		utils.MaxPeersFlag,
 		utils.MaxPendingPeersFlag,