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 and #23578 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 and #23578 

## Does this MR meet the acceptance criteria?

- [X] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [X] All builds are passing
- [X] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [X] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [X] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [X] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Closes #22058 and #23578 

See merge request !7129