Spawners, variables and active mobs should be saved asynchronously

Summary

Atm data is saved to files on the main server thread, this causes lag spikes on servers with a lot of mobs and spawners.

Priority

This is an important enhancement for large servers.

Implementation

I injected a custom implementation using RuntimeTransformer as a proof of concept:

• https://pastebin.com/medUVdLT
• https://pastebin.com/Kh9SaRHQ
• https://pastebin.com/vK8L2V0Q

public final class MythicMobsFixes extends JavaPlugin {

    @Override
    public void onLoad() {
        List<Class<?>> transformers = new ArrayList<>();
        transformers.add(MobManagerTransformer.class);
        transformers.add(SpawnerManagerTransformer.class);
        new RuntimeTransformer(transformers.toArray(new Class<?>[0]));
    }

    @Override
    public void onEnable() {
        Executors.getInstance(); // Cache executors
    }

    @Override
    public void onDisable() {
        Executors.shutdown();
    }
}