Reject use of fmt.Printf under cmd/ (#3570)

## Changes

Reject directly writing to global stdout/stderr.

The "forbidigo" linter includes this rule by default.

Also see https://golangci-lint.run/docs/linters/configuration/#forbidigo

## Why

The CLI uses Cobra and should therefore use `cmd.OutOrStdout()` and
friends.

Saw this here:
#3546 (comment)

Author: pietern

.golangci.yaml

@@ -16,6 +16,7 @@ linters:
     - unused
     - exhaustruct
     - copyloopvar
+    - forbidigo
   settings:
     copyloopvar:
       check-alias: true
@@ -72,6 +73,9 @@ linters:
       - path: bundle/terranova/tnresources/all_test.go
         linters:
           - exhaustruct
+      - path-except: ^cmd
+        linters:
+          - forbidigo
 issues:
   max-issues-per-linter: 1000
   max-same-issues: 1000

cmd/bundle/generate/dashboard.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"os"
 	"path"
 	"path/filepath"
@@ -53,6 +54,10 @@ type dashboard struct {
 
 	// Relative path from the resource directory to the dashboard directory.
 	relativeDashboardDir string
+
+	// Output and error streams.
+	out io.Writer
+	err io.Writer
 }
 
 func (d *dashboard) resolveID(ctx context.Context, b *bundle.Bundle) string {
@@ -185,7 +190,7 @@ func (d *dashboard) saveSerializedDashboard(_ context.Context, b *bundle.Bundle,
 		}
 	}
 
-	fmt.Printf("Writing dashboard to %q\n", rel)
+	fmt.Fprintf(d.out, "Writing dashboard to %q\n", rel)
 	return os.WriteFile(filename, data, 0o644)
 }
 
@@ -229,7 +234,7 @@ func (d *dashboard) saveConfiguration(ctx context.Context, b *bundle.Bundle, das
 		rel = resourcePath
 	}
 
-	fmt.Printf("Writing configuration to %q\n", rel)
+	fmt.Fprintf(d.out, "Writing configuration to %q\n", rel)
 	err = saver.SaveAsYAML(result, resourcePath, d.force)
 	if err != nil {
 		return err
@@ -462,7 +467,10 @@ The --watch flag continuously polls for remote changes and updates your local
 bundle files automatically, useful during active dashboard development.`,
 	}
 
-	d := &dashboard{}
+	d := &dashboard{
+		out: cmd.OutOrStdout(),
+		err: cmd.ErrOrStderr(),
+	}
 
 	// Lookup flags.
 	cmd.Flags().StringVar(&d.existingPath, "existing-path", "", `workspace path of the dashboard to generate configuration for`)