[AIO] Excess flood prevention

Regardless of the use case it is usually desired that a client/bot does not excess flood itself out of a network. This is a tricky problem to solve as networks have different ways of calculating how much is too much.

I have a downstream AIO solution that was scientifically calculated by trial-and-error on popular IRC networks with fair :game_die: rolls to land on an algorithm: https://github.com/hifi/heisenbridge/blob/master/heisenbridge/irc.py#L160

If such implementation is upstreamed it needs to be configurable and possibly off by default. Let me know if something can be worked out.

Start by reviewing the downstream implementation in heisenbridge/irc.py around line 160 and compare its assumptions with this library's IRC behavior. Determine the configurable behavior, network-specific limits, and default state with maintainers; done means an agreed upstream design is implemented and validated without imposing a fixed flood policy on every network.

Written by the indexing model from the issue text.