[iOS] Create an alert about the deletion of a downloaded video

[sergeymomot]

We need to add an alert when a downloaded video is deleted. To do this, first of all we need to create an alert, since at the moment such an alert does not exist.
We can use as a basis "Leave profile?" alert (can be found here: Profile -> Edit -> change something -> tap back).
Leave and Keep editing buttons should be replaced with Delete and Cancel buttons.
Icon can be used the same.
Alert text: something like "Are you sure you want to delete video(s) for "Module name" ?" (when deleting saved video for one module) and "Are you sure you want to delete video(s) for "Course name" ?" (when deleting all saved content by using the switch on the download panel).
Alert name: "Warning" , "Delete downloaded content?" or something else (can be discussed)