…#197290)

## Summary

This is a followup to the main Knowledge Base changes where we've:
1. Fixed the issue with access control to KB entries via bulk actions
APIs
2. Added the RBAC validation for the bulk actions API
3. Added integration tests to cover the bulk actions API

### Checklist

Delete any items that are not applicable to this PR.

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [x] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- Genai KB integration tests: [100 ESS + 100
Serverless](https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/7208)

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Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
(cherry picked from commit fd53861)