Potion effect hooks redux

I'd like to have potion effect hooks.

Currently you can tell a potion is active, but not when it's triggered. For example, the poison 1 effect only triggers once every 25 ticks based on the effect duration, dealing half a heart of damage when it does so. You can't currently hook when it triggers, but I would like that hook.

This is useful if, for example, you want to make potions last half as long, but trigger as they would normally; that is, half as many times as they'd trigger otherwise.

Such halving of potions would be implemented by ticking them twice every tick, but only letting the effect trigger every other time.

Other uses include changing the way effects are processed (poison gains regen-like abilities if you're zombie morph? regen damages you? etc).

The hook should be cancellable. The best place to put it is in PotionEffect.performEffect. The event needs to include the entity, and the effect itself.

An example mod that would use this hook is available here.