Zoekt: Return tasks in internal API

What does this MR do and why?

This MR adds zoekt_tasks to our Zoekt Internal API. This is needed to switch to a pull-based task model (right now we push tasks to Zoekt)

MR acceptance checklist

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DB queries

Click to see SQL to add tasks to postgres.ai

insert into zoekt_tasks (zoekt_node_id, zoekt_repository_id, project_identifier, perform_at, created_at, updated_at, task_type) select 4, 1, p.id, now(), now(), now(), 1 from generate_series(1,5000) as p(id);

Task processing query

SELECT "zoekt_tasks"."id",
       "zoekt_tasks"."zoekt_node_id",
       "zoekt_tasks"."zoekt_repository_id",
       "zoekt_tasks"."project_identifier",
       "zoekt_tasks"."perform_at",
       "zoekt_tasks"."created_at",
       "zoekt_tasks"."updated_at",
       "zoekt_tasks"."state",
       "zoekt_tasks"."task_type",
       "zoekt_tasks"."retries_left"
FROM "zoekt_tasks"
WHERE "zoekt_tasks"."zoekt_node_id" = 4
  AND "zoekt_tasks"."state" = 0
  AND "zoekt_tasks"."perform_at" >= '2024-02-26 11:26:54.873747'
ORDER BY "zoekt_tasks"."perform_at" ASC

https://postgres.ai/console/gitlab/gitlab-production-main/sessions/27234/commands/84716

Obsolete task update (100 batch size)

UPDATE "zoekt_tasks" SET "state" = 256 
WHERE "zoekt_tasks"."zoekt_node_id" = 4
  AND "zoekt_tasks"."state" = 0
  AND "zoekt_tasks"."perform_at" >= '2024-02-26 11:26:54.873747'
  AND "zoekt_tasks"."id" IN (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100)

https://postgres.ai/console/gitlab/gitlab-production-main/sessions/27234/commands/84721

Note: we don't have records on production. Locally it uses Index Scan

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Related to #424124 (closed)