Add trigger indexing worker

What does this MR do and why?

Related to #434590 (closed)

Behind a feature flag

Makes the gitlab:elastic:index rake task asynchronous through a new worker

Screenshots or screen recordings

N/A

How to set up and validate locally

1. setup gdk for elasticsearch
2. start elasticsearch

     gdk start elasticsearch

3. index everything, this will use the old method

     bundle exec rake gitlab:elastic:index

4. Go to Admin Area > Settings > Advanced Search to enable Elasticsearch.
   1. Elasticsearch indexing and Search with Elasticsearch enabled should be checked
5. confirm search works and is using Advanced search (should see a message: Advanced search is enabled)
6. enable the feature flag

      echo "Feature.enable(:elastic_index_use_trigger_indexing)" | gdk rails c

7. re-run the rake task

     bundle exec rake gitlab:elastic:index

8. confirm the worker runs successfully in the sidekiq logs
9. can also check status in **Admin Area > Settings > Advanced Search > Indexing status
10. confirm search works and is using Advanced search (should see a message: Advanced search is enabled)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

added groupglobal search typemaintenance labels

assigned to @dgruzd

added devopsdata stores sectioncore platform labels

added backend label

	1 Warning
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	1 Message
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Category	Reviewer	Maintainer
backend	@thutterer (UTC+1, same timezone as author)	@michold (UTC+1, same timezone as author)

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Sidekiq queue changes

This merge request contains changes to Sidekiq queues. Please follow the documentation on changing a queue's urgency.

These queues were added:

• search_elastic_trigger_indexing

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Generated by Danger

added 1 commit

• 5cf3f07a - fixup! Add trigger indexing worker

Compare with previous version

added feature flag label

added 1 commit

• 821aa23f - fixup! Add trigger indexing worker

Compare with previous version

mentioned in commit gitlab-org-sandbox/gitlab-jh-validation@ac208089

added 1 commit

• 8d81b20a - fixup! Add trigger indexing worker

Compare with previous version

mentioned in commit gitlab-org-sandbox/gitlab-jh-validation@21912bcd

E2E Test Result Summary

allure-report-publisher generated test report!

e2e-test-on-gdk: test report for 213e0404

expand test summary

+------------------------------------------------------------------+
|                          suites summary                          |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| Govern      | 64     | 0      | 3       | 0     | 67    | ✅     |
| Plan        | 51     | 0      | 3       | 0     | 54    | ✅     |
| Verify      | 29     | 0      | 2       | 0     | 31    | ✅     |
| Create      | 45     | 0      | 17      | 0     | 62    | ✅     |
| Package     | 15     | 0      | 1       | 0     | 16    | ✅     |
| Data Stores | 20     | 0      | 3       | 0     | 23    | ✅     |
| Monitor     | 7      | 0      | 0       | 0     | 7     | ✅     |
| Release     | 5      | 0      | 0       | 0     | 5     | ✅     |
| Manage      | 0      | 0      | 1       | 0     | 1     | ➖     |
| Analytics   | 2      | 0      | 0       | 0     | 2     | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 238    | 0      | 30      | 0     | 268   | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+

e2e-package-and-test: test report for af22f4ac

expand test summary

+---------------------------------------------------------------------+
|                           suites summary                            |
+----------------+--------+--------+---------+-------+-------+--------+
|                | passed | failed | skipped | flaky | total | result |
+----------------+--------+--------+---------+-------+-------+--------+
| Plan           | 246    | 0      | 13      | 3     | 259   | ✅     |
| Fulfillment    | 8      | 0      | 69      | 0     | 77    | ✅     |
| Govern         | 277    | 0      | 20      | 7     | 297   | ✅     |
| Package        | 226    | 0      | 17      | 0     | 243   | ✅     |
| Create         | 550    | 0      | 67      | 8     | 617   | ✅     |
| Systems        | 8      | 0      | 0       | 0     | 8     | ✅     |
| Analytics      | 7      | 0      | 0       | 0     | 7     | ✅     |
| GitLab Metrics | 2      | 0      | 1       | 0     | 3     | ✅     |
| Verify         | 138    | 0      | 27      | 6     | 165   | ✅     |
| Manage         | 39     | 1      | 10      | 4     | 50    | ❌     |
| Monitor        | 36     | 0      | 13      | 0     | 49    | ✅     |
| Data Stores    | 113    | 0      | 7       | 0     | 120   | ✅     |
| Configure      | 1      | 0      | 9       | 0     | 10    | ✅     |
| Secure         | 6      | 0      | 3       | 0     | 9     | ✅     |
| ModelOps       | 0      | 0      | 8       | 0     | 8     | ➖     |
| Release        | 15     | 0      | 3       | 0     | 18    | ✅     |
| Growth         | 0      | 0      | 6       | 0     | 6     | ➖     |
+----------------+--------+--------+---------+-------+-------+--------+
| Total          | 1672   | 1      | 273     | 28    | 1946  | ❌     |
+----------------+--------+--------+---------+-------+-------+--------+

cc @terrichu

I believe this worker can help with Support all projects indexed in elastic rake (!138098 - merged)

changed the description

changed milestone to %Backlog

changed milestone to %16.7

added 2 commits

• ace89e02 - fixup! Add trigger indexing worker
• e13654d5 - fixup! Add trigger indexing worker

Compare with previous version

mentioned in commit gitlab-org-sandbox/gitlab-jh-validation@7f24d31e