[8.19] Fixing flaky alert deletion tests (#226281) (#226442)

# Backport

This will backport the following commits from `main` to `8.19`:
- [Fixing flaky `alert deletion` tests
(#226281)](#226281)

<!--- Backport version: 9.6.6 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sorenlouv/backport)

<!--BACKPORT [{"author":{"name":"Ying
Mao","email":"[email protected]"},"sourceCommit":{"committedDate":"2025-07-03T14:07:00Z","message":"Fixing
flaky `alert deletion` tests (#226281)\n\nFixes
https://github.com/elastic/kibana/issues/226076\nFixes
https://github.com/elastic/kibana/issues/226074\nFixes
https://github.com/elastic/kibana/issues/225725\nFixes
https://github.com/elastic/kibana/issues/225280\nFixes
https://github.com/elastic/kibana/issues/224985\nFixes
https://github.com/elastic/kibana/issues/224934\nFixes
https://github.com/elastic/kibana/issues/224742\nFixes
https://github.com/elastic/kibana/issues/224675\nFixes
https://github.com/elastic/kibana/issues/224670\n\nFixes
https://github.com/elastic/kibana/issues/224135\nFixes
https://github.com/elastic/kibana/issues/223437\nFixes
https://github.com/elastic/kibana/issues/223364\n\n## Summary\n\nThe
first 9 issues were flaky with error `Error: expected 200 to sort
of\nequal 204`. This is caused by this
PR\nhttps://github.com//pull/223336 which has the schedule
API\nreturn a 200 if an instance of the task was already running for
the\nspace. This flakiness should be fixed by retrying the schedule
request\nuntil a 204 is achieved.\n\nThe last 3 issues were flaky before
the prior PR was merged so I suspect\nthey ran into the same issue
(where another instance of the task was\nalready running so the new task
was not kicked off but no indication of\nthis was
returned).","sha":"10a540bf4afda4c51f5c218fd1169e7a2483246d","branchLabelMapping":{"^v9.2.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["Feature:Alerting","release_note:skip","Team:ResponseOps","backport:version","v9.1.0","v8.19.0","v9.2.0"],"title":"Fixing
flaky `alert deletion`
tests","number":226281,"url":"https://github.com/elastic/kibana/pull/226281","mergeCommit":{"message":"Fixing
flaky `alert deletion` tests (#226281)\n\nFixes
https://github.com/elastic/kibana/issues/226076\nFixes
https://github.com/elastic/kibana/issues/226074\nFixes
https://github.com/elastic/kibana/issues/225725\nFixes
https://github.com/elastic/kibana/issues/225280\nFixes
https://github.com/elastic/kibana/issues/224985\nFixes
https://github.com/elastic/kibana/issues/224934\nFixes
https://github.com/elastic/kibana/issues/224742\nFixes
https://github.com/elastic/kibana/issues/224675\nFixes
https://github.com/elastic/kibana/issues/224670\n\nFixes
https://github.com/elastic/kibana/issues/224135\nFixes
https://github.com/elastic/kibana/issues/223437\nFixes
https://github.com/elastic/kibana/issues/223364\n\n## Summary\n\nThe
first 9 issues were flaky with error `Error: expected 200 to sort
of\nequal 204`. This is caused by this
PR\nhttps://github.com//pull/223336 which has the schedule
API\nreturn a 200 if an instance of the task was already running for
the\nspace. This flakiness should be fixed by retrying the schedule
request\nuntil a 204 is achieved.\n\nThe last 3 issues were flaky before
the prior PR was merged so I suspect\nthey ran into the same issue
(where another instance of the task was\nalready running so the new task
was not kicked off but no indication of\nthis was
returned).","sha":"10a540bf4afda4c51f5c218fd1169e7a2483246d"}},"sourceBranch":"main","suggestedTargetBranches":["9.1","8.19"],"targetPullRequestStates":[{"branch":"9.1","label":"v9.1.0","branchLabelMappingKey":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"},{"branch":"8.19","label":"v8.19.0","branchLabelMappingKey":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"},{"branch":"main","label":"v9.2.0","branchLabelMappingKey":"^v9.2.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/226281","number":226281,"mergeCommit":{"message":"Fixing
flaky `alert deletion` tests (#226281)\n\nFixes
https://github.com/elastic/kibana/issues/226076\nFixes
https://github.com/elastic/kibana/issues/226074\nFixes
https://github.com/elastic/kibana/issues/225725\nFixes
https://github.com/elastic/kibana/issues/225280\nFixes
https://github.com/elastic/kibana/issues/224985\nFixes
https://github.com/elastic/kibana/issues/224934\nFixes
https://github.com/elastic/kibana/issues/224742\nFixes
https://github.com/elastic/kibana/issues/224675\nFixes
https://github.com/elastic/kibana/issues/224670\n\nFixes
https://github.com/elastic/kibana/issues/224135\nFixes
https://github.com/elastic/kibana/issues/223437\nFixes
https://github.com/elastic/kibana/issues/223364\n\n## Summary\n\nThe
first 9 issues were flaky with error `Error: expected 200 to sort
of\nequal 204`. This is caused by this
PR\nhttps://github.com//pull/223336 which has the schedule
API\nreturn a 200 if an instance of the task was already running for
the\nspace. This flakiness should be fixed by retrying the schedule
request\nuntil a 204 is achieved.\n\nThe last 3 issues were flaky before
the prior PR was merged so I suspect\nthey ran into the same issue
(where another instance of the task was\nalready running so the new task
was not kicked off but no indication of\nthis was
returned).","sha":"10a540bf4afda4c51f5c218fd1169e7a2483246d"}}]}]
BACKPORT-->

Co-authored-by: Ying Mao <[email protected]>

Author: kibanamachine