Refactor emoji helpers in preparation for async loading

What does this MR do?

Centralizes emoji helper methods so that we can eventually split them into their own on-demand chunk

I'm splitting this into a separate, more-focused MR from !12032 (merged) and once this is merged, I can rebase that work on top of this.

Are there points in the code the reviewer needs to double check?

Emoji functionality should still work as expected.

Why was this MR needed?

Paving the way to remove the gigantic digests.json file from our main bundle to speed up initial page loads.

Screenshots (if relevant)

n/a

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

related to #33391 (closed)