Combine last_activity_at and last_repository_updated_at updates for projects into a single statement

The following two queries were identified in https://gitlab.com/gitlab-com/gitlab-OKRs/-/work_items/7859 as top contributors to the WAL generated as a results of projects table activity:

-- reset_project_activity
UPDATE
        "projects"
SET
        "updated_at" = $ 1,
        "last_activity_at" = $ 2
WHERE
        "projects"."id" = $ 3
        AND (last_activity_at <= $ 4)

-- set_last_repository_updated_at
UPDATE
        "projects"
SET
        "updated_at" = $ 1,
        "last_repository_updated_at" = $ 2
WHERE
        "projects"."id" = $ 3
        AND (
                last_repository_updated_at < $ 4
                OR last_repository_updated_at IS NULL
        )

Proposal

Combine these updates into a single statement so that write amplification cost is paid only once.