Migrate to `emmylua_ls`

https://github.com/EmmyLuaLs/emmylua-analyzer-rust

This LSP has some noticeable differences compared to LuaLS, for example using `---@module` annotations.

It will be a bit of a pain to adjust these annotations throughout the codebase to satisfy the type checker.

Will need to start playing around and decide if it is worth doing.