Merge branch '509055-show-var-description-in-the-dropdown' into 'master'

Show variable description in the dropdown

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/175843



Merged-by: Kos Palchyk <kpalchyk@gitlab.com>
Approved-by: Fernanda Toledo <ftoledo@gitlab.com>
Approved-by: Kos Palchyk <kpalchyk@gitlab.com>
Reviewed-by: Kos Palchyk <kpalchyk@gitlab.com>
Reviewed-by: Chen Charnolevsky <ccharnolevsky@gitlab.com>
Reviewed-by: Fernanda Toledo <ftoledo@gitlab.com>
Co-authored-by: Chen Charnolevsky <ccharnolevsky@gitlab.com>