Start using new table for instance integrations (using feature flag)
<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=474812) </details> <!--IssueSummary end--> As part of https://gitlab.com/groups/gitlab-org/-/epics/14638 at this point we should have identical amount of records of instance integrations in `integrations` table and mirroring records in `instance_integrations` tables, which should be ready to perform a swap of using integrations to instance_integrations. ### Proposed solution 1. Update existing usages of instance integrations that use `integrations` records to use `instance_integrations` 2. Add a feature flag to swap to the new table records
issue