Fix rendering emoji inside a string

What does this MR do?

1. It does not let emojis be rendered if they are surrounded by numbers (0-9), colon (:) or letters ([:alnum:]).
2. It lets emojis be rendered in all other cases.

Screenshots (if relevant)

Before	After

Write	Preview

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests
  • Added for this feature/bug
  • All builds are passing
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #26433 (closed)