Write all logging (INFO, WARN, ERROR) to stderr

The old setup tried to log >= warning to stderr, the rest to stdout.

However, that logic was flawed, so warnings ended up in stdout, which makes `hugo list all` etc. hard to reason about from scripts.

This commit fixes this by making all logging (info, warn, error) log to stderr and let stdout be reserved for program output.

Fixes #13074

commands/list.go

@@ -57,7 +57,7 @@ func newListCommand() *listCommand {
 			return err
 		}
 
-		writer := csv.NewWriter(r.Out)
+		writer := csv.NewWriter(r.StdOut)
 		defer writer.Flush()
 
 		writer.Write([]string{