Merge branch '442091-basic-search' into 'master'

User autocomplete scoped to authorized namespaces for Basic Search

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/182557



Merged-by: Madelein van Niekerk <mvanniekerk@gitlab.com>
Approved-by: Tiger Watson <twatson@gitlab.com>
Approved-by: Ravi Kumar <rkumar@gitlab.com>
Approved-by: Terri Chu <tchu@gitlab.com>
Reviewed-by: Tiger Watson <twatson@gitlab.com>
Reviewed-by: Terri Chu <tchu@gitlab.com>