Improve plugin load speed

When first opening neovim with lazy.nvim, it seems like distant takes the most time to load of any plugin I use. I think this is because we're using `init.lua` to pre-load all of the modules. Instead, we should switch to using `require` calls to the specific module.

This seems to be much less of a painpoint when using `vim.loader.enable()` for neovim 0.9+, but still something to look into improving.