Include Discord's stock and custom emoji in tab-completion menu

[noodlebox]

The current implementation completely overrides the default emoji tab-completion behavior. One option is to permit the default tab-completion behavior when no matches are found, but this is clunky-looking and more prone to breakage. Ideally, we would be able to use the improved menu for everything, for consistent sorting behavior and scroll-able results.

In order to include the default emoji they will need to be enumerable, with the most likely source of this data being EmojiPicker in state.metaData when active. Hopefully, there's a better alternative somewhere else. Making our own API calls is possible, though less desirable, and this would only include custom emoji.

[noodlebox]

This may open up more options for getting (and modifying) information about stock emotes: https://gist.github.com/samogot/736dc6289c9fdb9d1f12aba253d530f5