Add/remove changed suggested emojis for internal channels on restart

[chandler05]

Purpose

On restart, refresh the new or removed suggested emojis for all internal channel messages.

Notes

This does not slow down initialization, but I'm not sure if this is the worth having a feature for. I only added this since the suggested emojis are configurable and if the bot were usable on other servers and someone changed the emojis, they'd probably expect the old messages to change as well.

This potentially implements #202 if we don't want to refresh the embeds as well.

[violine1101]

Adding emojis is painfully slow because Discord's rate limiting in this regard is ridiculous. When we add an emoji here, it could very well take the bot multiple hours to have added the new emojis, depending on the amount of existing pending requests. The alternative is just adding the emoji manually.

Not sure if it's really worth the hassle tbh.

Ultimately we can replace the reactions with the fancy new buttons, which will be even better anyway.

[chandler05]

Buttons sound nice