Add basic auth to Zoekt client

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127203



Merged-by: John Mason <9717668-johnmason@users.noreply.gitlab.com>
Approved-by: John Mason <9717668-johnmason@users.noreply.gitlab.com>
Approved-by: Siddharth Dungarwal <sdungarwal@gitlab.com>
Co-authored-by: Dylan Griffith <dyl.griffith@gmail.com>