Lazy loading on Paginators

[ByteAlex]

Summary

Paginators should support lazy loading pages with either "infinite scroll" or a fixed ending.

Current Behaviour

Pages need to be predefined from the creation of the message.

Preferred Behaviour

Pages should be lazy loaded as a user may click through them.

Reasoning

A database may be large; for example a leaderboard. You need a sorted subset of it, but not all data at once. That saves a lot of traffic and cpu cycles for data which most likely is never been seen anyway... Who is gonna click the "next page" 25 times every time they open the leaderboard, right?