Replace advancement trigger with events

Currently advancements are triggered by advancement triggers, while simple and straight-forward, it limits the power of data packs with incomplete game events detection.

The idea is to separate the functionality using "events", with following features:

1. Same as advancements, events are defined in json files under namespace/events/

2. "Events" can be called in advancements and works just like triggers, but can also be triggered separately and call mcfunctions.

3. While current current advancement triggers should be modified and made more consistent, "events" should also contain more basic game events such as player input (like mouse clicks).

With events, the capability of data packs could be largely expanded to even replace server plugins (which obviously is beneficial in many ways).