[TASK] allow specifying multiple --metadata values directly

[JoernBerkefeld]

right now, if you want to specify more than one type/key you need to do sth like this:

mcdev retrieve cred/bu -m dataExtension -m query

by setting the property array: true in metadata-option's config. we instead allow this as well:

mcdev retrieve cred/bu -m dataExtension query

--> no need to repeat -m

[github-actions]

Closed by #1445.