dashboard: remove the dashboard (#20279)

This removes the dashboard project. The dashboard was an experimental
browser UI for geth which displayed metrics and chain information in
real time. We are removing it because it has marginal utility and nobody
on the team can maintain it.

Removing the dashboard removes a lot of dependency code and shaves
6 MB off the geth binary size.

cmd/geth/main.go

@@ -70,10 +70,6 @@ var (
 		utils.NoUSBFlag,
 		utils.SmartCardDaemonPathFlag,
 		utils.OverrideIstanbulFlag,
-		utils.DashboardEnabledFlag,
-		utils.DashboardAddrFlag,
-		utils.DashboardPortFlag,
-		utils.DashboardRefreshFlag,
 		utils.EthashCacheDirFlag,
 		utils.EthashCachesInMemoryFlag,
 		utils.EthashCachesOnDiskFlag,
@@ -236,16 +232,8 @@ func init() {
 	app.Flags = append(app.Flags, metricsFlags...)
 
 	app.Before = func(ctx *cli.Context) error {
-		logdir := ""
-		if ctx.GlobalBool(utils.DashboardEnabledFlag.Name) {
-			logdir = (&node.Config{DataDir: utils.MakeDataDir(ctx)}).ResolvePath("logs")
-		}
-		if err := debug.Setup(ctx, logdir); err != nil {
-			return err
-		}
-		return nil
+		return debug.Setup(ctx, "")
 	}
-
 	app.After = func(ctx *cli.Context) error {
 		debug.Exit()
 		console.Stdin.Close() // Resets terminal mode.