Fixes: #19687
The --quiet options to gitea dump silences informational and less
important messages, but will still log warnings and errors to console.
Very useful in combination with cron backups and '-f -'.
Since --verbose and --quiet are incompatible with each other I made it
an error to specify both. To get the error message to be printed to
stderr I had to make this test after the NewServices()-call, which is
why there are three new blocks of code instead of two.