Uniform representation of emoji (#2117)* Rename MessageReaction#getReactionEmote* Add Emote#getOwner* Add Emote#retrieveOwner* Restructure hierarchy and rename Emote to CustomEmoji* Add Emoji#getFormatted* Rename Emoji#fromMarkdown to Emoji#fromFormatted* Remove RichCustomEmoji#canProvideRoles* Make RichCustomEmoji#getGuild never-null* Handle permissions for RichCustomEmoji#retrieveOwner* Add sticker events to GatewayIntent#fromEvents* Allow setting role icon with UnicodeEmoji (commit: 2150f0f)