Consistent emoji representation in forum tags

[MinnDevelopment]

In #5391, the available_tags feature has been documented, which introduces a new Forum Tag Object and Default Reaction Object. Unlike reactions and guild custom emoji, these do not use the standard emoji object layout of name, id, animated. Instead, they have an emoji_name and emoji_id field, which are mutually exclusive.

I'd prefer if this was more standardised and always provided a partial emoji, similar to reactions:

Custom:

"emoji": {
  "id": 123,
  "name": "chillin",
  "animated": true
}

Unicode:

"emoji": {
  "name": "❤"
}

That is consistent with:

• Activity.emoji
• Reaction.emoji
• Button.emoji
• SelectOption.emoji
• Guild.emoji

[advaith1]

wanted to note that welcome screen channels also use emoji_id and emoji_name, although it properly includes emoji_name for custom emojis, unlike forums.