[AUTO] Add release notes for 3.6.0

[opensearch-ci-bot]

Add release notes for 3.6.0

Borderline Calls

• Add Target object for external data source support on Monitor and Alert models. #916 and Revert "Add Target object for external data source support on Monitor and Alert (#916)" #917: PR Add Target object for external data source support on Monitor and Alert models. #916 adds the Target object feature and PR Revert "Add Target object for external data source support on Monitor and Alert (#916)" #917 reverts it. Both are included since they are separate commits. Add Target object for external data source support on Monitor and Alert models. #916 is placed in Features and Revert "Add Target object for external data source support on Monitor and Alert (#916)" #917 in Bug Fixes (as a revert correcting an issue). An alternative would be to omit both or place Revert "Add Target object for external data source support on Monitor and Alert (#916)" #917 in Maintenance.
• Validate api_type matches path in ClusterMetricsInput #912: Placed in Enhancements — could also be Bug Fixes since it fixes a scenario where mismatched api_type and path could create undeletable monitors, but the change adds new validation logic to an existing feature rather than fixing broken behavior in the traditional sense.
• Remove hardcoded trigger limit from Monitor data class and make number of triggers per monitor configurable #913: Placed in Enhancements — could also be Refactoring since it moves validation logic out of the data class, but the user-facing impact is that trigger limits are now configurable, which is an enhancement.
• Update shadow plugin usage #904: Placed in Infrastructure — borderline with Maintenance, chose Infrastructure because it modifies build tooling configuration rather than updating a dependency version.