log, internal/debug: delete RotatingFileHandler (#20586)

* log: delete RotatingFileHandler

We added this for the dashboard, which is gone now. The
handler never really worked well and had data race and file
handling issues.

* internal/debug: remove unused RotatingFileHandler setup code

internal/debug/flags.go

@@ -112,20 +112,9 @@ func init() {
 
 // Setup initializes profiling and logging based on the CLI flags.
 // It should be called as early as possible in the program.
-func Setup(ctx *cli.Context, logdir string) error {
+func Setup(ctx *cli.Context) error {
 	// logging
 	log.PrintOrigins(ctx.GlobalBool(debugFlag.Name))
-	if logdir != "" {
-		rfh, err := log.RotatingFileHandler(
-			logdir,
-			262144,
-			log.JSONFormatOrderedEx(false, true),
-		)
-		if err != nil {
-			return err
-		}
-		glogger.SetHandler(log.MultiHandler(ostream, rfh))
-	}
 	glogger.Verbosity(log.Lvl(ctx.GlobalInt(verbosityFlag.Name)))
 	glogger.Vmodule(ctx.GlobalString(vmoduleFlag.Name))
 	glogger.BacktraceAt(ctx.GlobalString(backtraceAtFlag.Name))