Completely rework event system

* Event instances are now generated dynamically at runtime. The performance hit of creating proxies at runtime is negligible in this case.

* A better EventBus implementation is now being used internally, API contracts are unaffected.

sponge/src/main/java/me/lucko/luckperms/sponge/LPSpongePlugin.java

@@ -112,7 +112,7 @@ public class LPSpongePlugin extends AbstractLuckPermsPlugin {
 
     @Override
     protected Set<Dependency> getGlobalDependencies() {
-        return EnumSet.of(Dependency.TEXT, Dependency.CAFFEINE, Dependency.OKIO, Dependency.OKHTTP,
+        return EnumSet.of(Dependency.TEXT, Dependency.CAFFEINE, Dependency.OKIO, Dependency.OKHTTP, Dependency.EVENT,
                 Dependency.CONFIGURATE_CORE, Dependency.CONFIGURATE_HOCON, Dependency.HOCON_CONFIG);
     }