Use GroupPlansPreloader linear ancestor scopes

WITH RECURSIVE "base_and_ancestors" AS (
                                          (SELECT "namespaces".*
                                           FROM "namespaces"
                                           WHERE "namespaces"."type" = 'Group'
                                             AND "namespaces"."id" IN (1,2))
                                        UNION
                                          (SELECT "namespaces".*
                                           FROM "namespaces",
                                                "base_and_ancestors"
                                           WHERE "namespaces"."type" = 'Group'
                                             AND "namespaces"."id" = "base_and_ancestors"."parent_id"))
SELECT "namespaces"."id",
       "namespaces"."parent_id",
       "gitlab_subscriptions"."hosted_plan_id"
FROM "base_and_ancestors" AS "namespaces"
LEFT OUTER JOIN gitlab_subscriptions ON gitlab_subscriptions.namespace_id=namespaces.id

Time: 6.501 ms
  - planning: 2.708 ms
  - execution: 3.793 ms
    - I/O read: 0.000 ms
    - I/O write: 0.000 ms

Shared buffers:
  - hits: 740 (~5.80 MiB) from the buffer pool
  - reads: 0 from the OS file cache, including disk I/O
  - dirtied: 0
  - writes: 0

SELECT "namespaces"."id",
       "namespaces"."parent_id",
       "gitlab_subscriptions"."hosted_plan_id"
FROM
  (SELECT "namespaces".*
   FROM "namespaces"
   WHERE "namespaces"."id" IN
       (SELECT unnest(traversal_ids)
        FROM "namespaces"
        WHERE "namespaces"."id" IN (1,2))) namespaces
LEFT OUTER JOIN gitlab_subscriptions ON gitlab_subscriptions.namespace_id=namespaces.id

Time: 2.699 ms
  - planning: 0.815 ms
  - execution: 1.884 ms
    - I/O read: 0.000 ms
    - I/O write: 0.000 ms

Shared buffers:
  - hits: 763 (~6.00 MiB) from the buffer pool
  - reads: 0 from the OS file cache, including disk I/O
  - dirtied: 0
  - writes: 0

Gitlab::GroupPlansPreloader.new.send(:groups_and_ancestors_for, Group.where(id: [1, 2]))