Zoekt: Add enable search dot_com_rollout subtask

What does this MR do and why?

This is a follow-up to Add Zoekt dot_com_rollout scheduling task (!144988 - merged)

In this MR we're automating enabling search for recently added namespaces (older than 72 hours). This is needed to automate CR's like 2024-02-14: Enable search for namespaces in Zoekt (gitlab-com/gl-infra/production#17591 - closed)

Database queries

UPDATE "zoekt_enabled_namespaces"
SET "search" = TRUE, "updated_at" = '2024-02-20 12:07:08.285461'
WHERE "zoekt_enabled_namespaces"."id" IN
    (SELECT "zoekt_enabled_namespaces"."id"
     FROM "zoekt_enabled_namespaces"
     WHERE "zoekt_enabled_namespaces"."search" = FALSE
       AND (created_at < '2024-02-17 12:07:08.285237')
     ORDER BY "zoekt_enabled_namespaces"."id" ASC
     LIMIT 100)

https://postgres.ai/console/gitlab/gitlab-production-tunnel-pg12/sessions/26537/commands/83091

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