cmd/utils, node: remove unused solc references and improve RPC config (#14324)

Currently http cors and websocket origins are a comma separated string in the
config object. These are replaced with string arrays that are more expressive in
case of a config file.

cmd/geth/main.go

@@ -140,7 +140,6 @@ func init() {
 		utils.MetricsEnabledFlag,
 		utils.FakePoWFlag,
 		utils.NoCompactionFlag,
-		utils.SolcPathFlag,
 		utils.GpoBlocksFlag,
 		utils.GpoPercentileFlag,
 		utils.ExtraDataFlag,