Change auto selection behaviour of emoji and slash commands to be more UX/Type friendly

What does this MR do?

In the context of a special command (starting with "/", ":", ...), the MR disables auto selection of first item in the dropdown suggestion menu, until at least a character has been typed. This behavior change originated from #22058 (closed) and #23578 (closed) in which problems with the ":" special command were pointed out.

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

At lines +187 and +242 there were originally no sorters. Given what DefaultOptions.sorter does, I don't think it is a problem.

Why was this MR needed?

To solve #22058 (closed) and #23578 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• 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?

Closes #22058 (closed) and #23578 (closed)