Add --debug as shortcut for --log-level debug (#964)

## Changes
This PR exposes simpler interfaces to end users.

## Tests
<img width="724" alt="image"
src="https://github.com/databricks/cli/assets/259697/8bd25110-33f0-4197-8f00-2b8198c4aba6">

Author: nfx

cmd/root/logger.go

@@ -73,6 +73,7 @@ type logFlags struct {
 	file   flags.LogFileFlag
 	level  flags.LogLevelFlag
 	output flags.Output
+	debug  bool
 }
 
 func (f *logFlags) makeLogHandler(opts slog.HandlerOptions) (slog.Handler, error) {
@@ -95,6 +96,10 @@ func (f *logFlags) makeLogHandler(opts slog.HandlerOptions) (slog.Handler, error
 }
 
 func (f *logFlags) initializeContext(ctx context.Context) (context.Context, error) {
+	if f.debug {
+		f.level.Set("debug")
+	}
+
 	opts := slog.HandlerOptions{}
 	opts.Level = f.level.Level()
 	opts.AddSource = true
@@ -137,9 +142,17 @@ func initLogFlags(cmd *cobra.Command) *logFlags {
 		f.output.Set(v)
 	}
 
-	cmd.PersistentFlags().Var(&f.file, "log-file", "file to write logs to")
-	cmd.PersistentFlags().Var(&f.level, "log-level", "log level")
-	cmd.PersistentFlags().Var(&f.output, "log-format", "log output format (text or json)")
+	flags := cmd.PersistentFlags()
+	flags.BoolVar(&f.debug, "debug", false, "enable debug logging")
+	flags.Var(&f.file, "log-file", "file to write logs to")
+	flags.Var(&f.level, "log-level", "log level")
+	flags.Var(&f.output, "log-format", "log output format (text or json)")
+
+	// mark fine-grained flags hidden from global --help
+	flags.MarkHidden("log-file")
+	flags.MarkHidden("log-level")
+	flags.MarkHidden("log-format")
+
 	cmd.RegisterFlagCompletionFunc("log-file", f.file.Complete)
 	cmd.RegisterFlagCompletionFunc("log-level", f.level.Complete)
 	cmd.RegisterFlagCompletionFunc("log-format", f.output.Complete)