[8.9] [Security Solution] Flaky Cypress test: Detection rules, Prebuilt Rules Installation and Update workflow - Installation of prebuilt rules package via Fleet should install package from Fleet in the background

[jpdjere]

NOTE: This is a manual backport of #163468 to 8.9.

Original PR description:

Fixes: #163447
Fixes: #163586

Summary

• Fixes flaky test: x-pack/plugins/security_solution/cypress/e2e/detection_response/prebuilt_rules/prebuilt_rules_install_update_workflows.cy.ts
• Test title: Detection rules, Prebuilt Rules Installation and Update workflow - Installation of prebuilt rules package via Fleet should install package from Fleet in the background

Details

• Initially ran the flaky test runner with multiple iterations and all gave succesful results, i.e. no flakiness or failed tests.
• But: after checking the logs for the failed tests in the original failed build, discovered that the reason the test failed is because:
  • when checking Fleet's response for the installation of the security_detection_engine, the API response was not as expected from the API spec:

**Expected:** [{ name: 'security_detection_engine', installSource: 'registry' }]
**Actual:** [{ name: 'security_detection_engine', installSource: undefined }]

Since we cannot rely 100% that the Fleet API will return the correct value for the installSource, this PR deletes this part of the test to prevent any type of flakiness caused by external factors such as this.

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[elasticmachine]

Pinging @elastic/security-detections-response (Team:Detections and Resp)

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 4d6e602

Failed CI Steps

• Security Solution Tests #3
• Defend Workflows Cypress Tests #1

Test Failures

• [job] [logs] Security Solution Tests #3 / Changing alert status Opening alerts Open one alert when more than one closed alerts are selected
• [job] [logs] Defend Workflows Cypress Tests #1 / Endpoint Policy Response from Fleet Agent Details page should display policy response with errors

Metrics [docs]

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	13	15	+2
securitySolution	416	420	+4
total			+6

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	14	16	+2
securitySolution	497	501	+4
total			+6

History

• 💔 Build #152725 failed 1fa45c4

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @jpdjere