cmd: group network and db path flags together (#24698)

This PR groups all built-in network flags together and list them in the command as a whole.

And all database path flags(datadir, ancient) are also grouped, since usually these two are
used together.

cmd/utils/flags.go

@@ -144,17 +144,17 @@ var (
 		Name:  "mainnet",
 		Usage: "Ethereum mainnet",
 	}
-	GoerliFlag = cli.BoolFlag{
-		Name:  "goerli",
-		Usage: "Görli network: pre-configured proof-of-authority test network",
+	RopstenFlag = cli.BoolFlag{
+		Name:  "ropsten",
+		Usage: "Ropsten network: pre-configured proof-of-work test network",
 	}
 	RinkebyFlag = cli.BoolFlag{
 		Name:  "rinkeby",
 		Usage: "Rinkeby network: pre-configured proof-of-authority test network",
 	}
-	RopstenFlag = cli.BoolFlag{
-		Name:  "ropsten",
-		Usage: "Ropsten network: pre-configured proof-of-work test network",
+	GoerliFlag = cli.BoolFlag{
+		Name:  "goerli",
+		Usage: "Görli network: pre-configured proof-of-authority test network",
 	}
 	SepoliaFlag = cli.BoolFlag{
 		Name:  "sepolia",
@@ -823,6 +823,36 @@ var (
 	}
 )
 
+var (
+	// TestnetFlags is the flag group of all built-in supported testnets.
+	TestnetFlags = []cli.Flag{
+		RopstenFlag,
+		RinkebyFlag,
+		GoerliFlag,
+		SepoliaFlag,
+		KilnFlag,
+	}
+	// NetworkFlags is the flag group of all built-in supported networks.
+	NetworkFlags = append([]cli.Flag{
+		MainnetFlag,
+	}, TestnetFlags...)
+
+	// DatabasePathFlags is the flag group of all database path flags.
+	DatabasePathFlags = []cli.Flag{
+		DataDirFlag,
+		AncientFlag,
+	}
+)
+
+// GroupFlags combines the given flag slices together and returns the merged one.
+func GroupFlags(groups ...[]cli.Flag) []cli.Flag {
+	var ret []cli.Flag
+	for _, group := range groups {
+		ret = append(ret, group...)
+	}
+	return ret
+}
+
 // MakeDataDir retrieves the currently requested data directory, terminating
 // if none (or the empty string) is specified. If the node is starting a testnet,
 // then a subdirectory of the specified datadir will be used.