fix: Multiple network flags should prevent the BN to start (#14169)

* Implement Initial Logic

* Include check in main.go

* Add tests for multiple flags

* remove usage of append

* remove config/features dependency

* Move ValidateNetworkFlags to config/features

* Nit

* removed NetworkFlags from cmd

* remove usage of empty string literal

* add comment

* add flag validation to prysctl validator-exit

---------

Co-authored-by: Manu NALEPA <enalepa@offchainlabs.com>

cmd/beacon-chain/main.go

@@ -212,6 +212,10 @@ func before(ctx *cli.Context) error {
 		return errors.Wrap(err, "failed to set max fd limits")
 	}
 
+	if err := features.ValidateNetworkFlags(ctx); err != nil {
+		return errors.Wrap(err, "provided multiple network flags")
+	}
+
 	return cmd.ValidateNoArgs(ctx)
 }
 

cmd/prysmctl/validator/cmd.go

@@ -175,6 +175,9 @@ var Commands = []*cli.Command{
 					if err := cmd.LoadFlagsFromConfig(cliCtx, cliCtx.Command.Flags); err != nil {
 						return err
 					}
+					if err := features.ValidateNetworkFlags(cliCtx); err != nil {
+						return err
+					}
 					if err := tos.VerifyTosAcceptedOrPrompt(cliCtx); err != nil {
 						return err
 					}

cmd/validator/main.go

@@ -193,6 +193,10 @@ func main() {
 				return errors.Wrap(err, "failed to setup debug")
 			}
 
+			if err := features.ValidateNetworkFlags(ctx); err != nil {
+				return errors.Wrap(err, "provided multiple network flags")
+			}
+
 			return cmd.ValidateNoArgs(ctx)
 		},
 		After: func(ctx *cli.Context) error {