Deprecate FMLJavaModLoadingContext for removal

[dima-dencep]

As requested.

How do we handle this after getModEventBus got removed?

• https://github.com/neoforged/FancyModLoader/blob/main/languages/java/src/main/java/net/neoforged/fml/common/Mod.java#L81

What about updating other javadocs that have this method?

[Technici4n]

How do we handle this after getModEventBus got removed?

IMO we can remove the supplier from Mod.EventBusSubscriber.Bus, and instead pass the mod bus to AutomaticEventSubscriber#inject.

What about updating other javadocs that have this method?

I would suggest linking ModContainer#getEventBus instead. But we are going to look into moving most events to the normal forge bus soon:TM:, so we can leave the old javadoc in place since it will have to change anyway.