ip_cleanup_scheduler: Make IP and session retention configurable

[kescherCode]

In #6474, there are mentions of IP addresses being stored for too long (1 year). While this pull request doesn't allow disabling the storage of IP addresses, it would allow instance admins to limit the duration for which IP addresses are stored. In my Catstodon fork, I have deployed and tested these changes already, with success (with an IP address retention of 24 hours, and the Sidekiq job set to run every hour).

This pull request may require the following changes, but I am unsure how to best do them:

• another env config variable for defining how often the ip_cleanup_scheduler sidekiq job should be run, instead of having to modify sidekiq.yml directly. Or perhaps deriving an optimal value it from IP_RETENTION_PERIOD.
• A split between handling ip cleanups, session cleanups/terminations and login activity cleanups/deletions, all based on time. Currently, ip_cleanup_scheduler.rb handles all of these.

If this pull request is merged, the docs over at Configuring your environment will also need to be updated.

[koutsie]

lgtm, documentation needs to be updated to reflect thought.

[shleeable]

@kescherCode Is this only removing the historical data? or will this make people login after the retention period?

[kescherCode]

@shleeable Only removes historical data (and sessions not updated for a year, which is the current behaviour of Mastodon)