Handle orphaned zoekt repos

What does this MR do and why?

This relates to this epic: &14886 (closed)

This is based on the MR to handle orphaned indices !164222 (merged)

Closes #485806 (closed)

Search::Zoekt::Repository.should_be_marked_as_orphaned

https://postgres.ai/console/gitlab/gitlab-production-main/sessions/31375/commands/97410

SELECT "zoekt_repositories".* FROM "zoekt_repositories" WHERE "zoekt_repositories"."project_id" IS NULL

Search::Zoekt::Repository.should_be_deleted

https://postgres.ai/console/gitlab/gitlab-production-main/sessions/31375/commands/97411

SELECT "zoekt_repositories".* FROM "zoekt_repositories" WHERE "zoekt_repositories"."state" IN (230, 240)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.