In the industry standard keymap, both deleting objects and collections were mapped to the same keys causing confusion when only collections could be deleted through the keymap. Other issues for outliner delete have been raised as well T67462

This adds a new delete operator to delete all selected objects and collections, accessible from both the keymap and context menu. Now any selected objects and collections are deleted when Delete is chosen from the keymap. This also updates the tooltip description which was previously undocumented.

I decided to leave the operator in the context menu twice, for objects and collections because the menu changes depending on what is selected. It would be good to make this smarter, but I think it would be better as part of a larger cleanup of the context menu.