Follow-up on expand redacting/post filtering search to include non ES results

While working on https://gitlab.com/gitlab-org/gitlab/issues/36438 we postponed some ~"technical debt" improvements.

Suggestions to work on:

• https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/320#note_302763194
• https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/320#note_302765425
• https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/320#note_302765646
• https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/320#note_302768032
• https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/321#note_302967590
• https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/321#note_302967594
• https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/321#note_302967595
• https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/321#note_302967598

Suggestions will be pasted here after the original MR is merged into master