Deleting a title that was still on someone's watchlist got it re-requested on the next sync and on
every sync after that, as the only thing sync looked at was the media status. Entries are now
recorded per user with the watchlistedAt timestamp Plex reportes, so an entry is acted on once.
Removing a title from the watchlist and adding it back produces a new timestamp, which is a new
entry, so it gets requested again. Shows track which seasons were handled, so new seasons still come
through and re-adding the series resets it.

fix 3222