[Task] Evaluate how to prevent drag & drop from different `non standard trees` into `standard trees` (asset,document,object)

[mattamon]

Currently it is possible to drag & drop elements from non standard trees into the standard trees which causes problems with update/reload/refresh operations

Maybe firing an event in the drop event so you can cancel the drop altogether. E.g. like https://github.com/pimcore/admin-ui-classic-bundle/blob/1.x/public/js/pimcore/events.js#L205

[github-actions]

Thanks a lot for reporting the issue. We did not consider the issue as "Pimcore:Priority", "Pimcore:ToDo" or "Pimcore:Backlog", so we're not going to work on that anytime soon. Please create a pull request to fix the issue if this is a bug report. We'll then review it as quickly as possible. If you're interested in contributing a feature, please contact us first here before creating a pull request. We'll then decide whether we'd accept it or not. Thanks for your understanding.