Consider getting rid of the torrents cleanup job in favour of a torrents priority map with a max size

[mickvandijke]

The torrents priority map would replace Tracker.torrents and will grow until the max size is met. Whenever a torrent in the map is used, it will move up in the priority order. Whenever a new torrent needs to be added or an existing torrent needs to grow in size, but the max size would be exceeded, torrents at the bottom of the priority list will be removed until there is enough space again.

Cons

• The torrents map will possibly contain inactive torrents.

Pros

• No longer need the intensive torrents cleanup job.
• More control over tracker memory usage. Although this can also be implemented as a separate feature for the existing solution.