next_page is not currently being returned on listings which is causing
the rclone listing code to go wrong. This was returned so is likely a
regression in Drime.
This changes the page counter to calculate using current_page and
last_page. last_page on the first page request is just current_page+1.
drime appears to be capping per_page to 200. as more pages are
requested, last_page increments by 1 until current_page = last_page