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.

eth/config.go

@@ -105,7 +105,6 @@ type Config struct {
 	EnablePreimageRecording bool
 
 	// Miscellaneous options
-	SolcPath  string
 	DocRoot   string `toml:"-"`
 	PowFake   bool   `toml:"-"`
 	PowTest   bool   `toml:"-"`