Reorganise Setup of Emojis and loading of digests.json

What does this MR do?

It reduces the parsed size of the main.js bundle by 308KB (currently biggest part in there) from 1.12MB at the moment.

• Put Emoji PNG's into public folder so no asset hashes are necessary as they anyhow don't change

• Remove those hashes and change value keys to shorter ones to reduce the size of the JSON (348KB -> 194KB)

• Load the JSON async and not bundle it up

• Cache the emoji info in the localstorage and retrieve it from there

• Remove the emoji bundle from the main bundle

Closes #39000 (closed)

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer