New created projects could inherit services from groups

What does this MR do?

We can now save integrations that belong to a group !39959 (merged).

When creating/importing a new project, the precedence to create new integrations is: closest integration from ancestors of the project, instance-level integration or template service.

Group-level integrations are under a feature flag group_level_integrations.

SQL queries

The query is based on two ideas: @lulalala's alternative of the previous code !32775 (comment 351633123) and the code to find the closest group integration https://gitlab.com/gitlab-org/gitlab/-/blob/23a90108/app/models/service.rb#L244-251, and also using UNION https://docs.gitlab.com/ee/development/sql.html#use-unions.

SELECT "services".*
FROM (
        (SELECT "services".*
         FROM "services"
         WHERE "services"."active" = TRUE
           AND "services"."instance" = TRUE)
      UNION
        (SELECT "services".*
         FROM "services"
         WHERE "services"."active" = TRUE
           AND "services"."template" = TRUE)
      UNION
        (SELECT "services".*
         FROM "services"
         WHERE "services"."active" = TRUE
           AND "services"."group_id" IN
             (WITH RECURSIVE "base_and_ancestors" AS (
                                                        (SELECT "namespaces".*
                                                         FROM "namespaces"
                                                         WHERE "namespaces"."type" = 'Group'
                                                           AND "namespaces"."id" = 3)
                                                      UNION
                                                        (SELECT "namespaces".*
                                                         FROM "namespaces",
                                                              "base_and_ancestors"
                                                         WHERE "namespaces"."type" = 'Group'
                                                           AND "namespaces"."id" = "base_and_ancestors"."parent_id")) SELECT "id"
              FROM "base_and_ancestors" AS "namespaces"))) services
ORDER BY TYPE ASC, array_position(array
                                    (WITH RECURSIVE "base_and_ancestors" AS (
                                                                               (SELECT "namespaces".*
                                                                                FROM "namespaces"
                                                                                WHERE "namespaces"."type" = 'Group'
                                                                                  AND "namespaces"."id" = 3)
                                                                             UNION
                                                                               (SELECT "namespaces".*
                                                                                FROM "namespaces", "base_and_ancestors"
                                                                                WHERE "namespaces"."type" = 'Group'
                                                                                  AND "namespaces"."id" = "base_and_ancestors"."parent_id")) SELECT "id"
                                     FROM "base_and_ancestors" AS "namespaces")::bigint[], services.group_id),
                   INSTANCE DESC;

Time: 32.406 ms
  - planning: 2.399 ms
  - execution: 30.007 ms
    - I/O read: 26.199 ms
    - I/O write: 0.000 ms

Shared buffers:
  - hits: 12 (~96.00 KiB) from the buffer pool
  - reads: 21 (~168.00 KiB) from the OS file cache, including disk I/O
  - dirtied: 14 (~112.00 KiB)
  - writes: 0

Query plan: https://explain.depesz.com/s/HsDN

Related to the first checkbox of #242012 (closed) and #244320 (closed)