[1.20.4] Ref: Events structure

[emyfops]

This pull request refactors the structure of the com.lambda.event.events files

• Grouped some local player related events together (LocalPlayerEvent.kt)
• Added more documentation for events I know for sure
• Replaced super abstract classes to sealed classes for consistency

I also removed all Event interfaces to events that are never triggered
The following example is based from this file

sealed class ClientEvent {
    /**
     * Triggered upon client initialization
     */
    class Startup : Event

    /**
     * Triggered upon client shutdown
     */
    class Shutdown : Event
}

This way of creating event classes prevent the accidental registration of unused (never posted to TaskFlow) events as seen here

The only edge case where this is allowed is when the super class shares functions or variables for all the inner classes (example)