[DOCS][ResponseOps][Alerting][8.19]: Fixes the note about CCS priv requirements for reporting and updates Kib 8.19 release notes

[nastasha-solomon]

Summary

Contributes to http://github.com/elastic/docs-content-internal/issues/514 by updating the 8.19 reporting docs and Kibana release notes. More specifically, this PR:

• Modifies the the third sentence in note about CCS priv requirements for reporting. Replaces the term "leader" with "local".
• Adds breaking change entries to the 8.19 Kibana release notes and the Kibana upgrade notes. This should make the change more visible to users who are upgrading to 8.19.

Corresponding fixes

• 9.1 reporting docs: [ResponseOps][Alerting][9.1]: Fixes the note about CCS priv requirements for reporting docs-content#4211
• 9.1 Kibana release notes: [DOCS][ResponseOps][Alerting][9.1]: Add breaking change to CCS-based reporting to 9.1 Kibana release notes #245183

Previews

• Automatically generate reports - Updated note
• Configure reporting in Kibana | Grant users access to reporting - Updated second note in intro
• Upgrade notes | Breaking changes | Kibana platform - Added entry titled "[Sharing & Reporting] API keys are used for authenticating report generation requests. (8.19)"
• Kibana 8.19.0 | Breaking changes - Added entry titled "API keys are used for authenticating report generation requests"

[github-actions]

A documentation preview will be available soon.

• 🔨 Buildkite builds
• 📚 HTML diff
• 📙 Preview page

Request a new doc build by commenting

• Rebuild this PR: run docs-build
• Rebuild this PR and all Elastic docs: run docs-build rebuild

_{run docs-build is much faster than run docs-build rebuild. A rebuild should only be needed in rare situations.}

_{If your PR continues to fail for an unknown reason, the doc build pipeline may be broken. Elastic employees can check the pipeline status here.}

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 5912486

cc @nastasha-solomon