batchDelete
Deletes all given localMediaItems from the local storage. This is a permanent delete that cannot be undone.
You should always favor this method over delete when deleting multiple items.
Note that this is not an atomic / transactional method. This means, that if some file fails to delete, all previously deleted files are already gone.
Scheduler: The returned Completable will operate on the IO Scheduler.
Return
a Completable which completes once all media items have been deleted (or errors if the action failed)
Parameters
localMediaItems
The list of MediaItem.Local to delete.