Attach clipboardjs with native querySelectorAll on context

In #3240131: Drupal.behavior gets attached multiple times instead of once, a check was added to prevent attaching multiple times. Unforunately, this also kills AJAX funktionallity, since AJAX will not pass in "document", but the respective element. Since we are loading the library on demand, this never gets executed since "document" never matches context.

Using context to pass in the detected elements to ClipboardJS seems the more suitable approach. Additionally, a "detach" function could be added to unregsiter possible clipboard events