Deduplicate identical custom emojis in the emoji picker

Problem

Currently in Fluxer (and also every other app with custom emotes), if you're in a bunch of servers that use the same custom emote, your emote picker UI will be clogged up with a bunch of duplicate emotes - on Discord I have like 10 of the same "+1" emotes.

Proposal

When a custom emote is created, scale it to a set resolution and create a simple hash of the bitmap, and store that with the rest of its metadata. Then, when loading the emote suggestions, deduplicate the list by the hash (or maybe the hash + the name, but that won't catch as much), prioritizing keeping emotes from the current server.