Remove eventManger module

[DecDuck]

There's no documentation and it seems pretty unused.

To remove we'd have to delete the module but then remove the hooks in scripts/mainThread/controller.lua

This technically would be a breaking change so we should consider deprecating first (but I don't think we have a large enough of a developer-base to justify it)

[SirLich]

Event manager is indeed quite old, and not that useful. I think the kernel of the idea is useful, but current implementation is not. I do believe I use it in one of my mods, but it should be easy to replace.

I do think it would be nice to resurrect as some kind of generic cross-thread RPC though, since I don't like shadowing server.lua to register the call.