Adding handling of FAILING_OVER and FAILED_OVER events/push notifications

[petyaslavova]

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Description of change

Adding handling of FAILING_OVER and FAILED_OVER events/push notifications

[Copilot]

Pull Request Overview

This PR extends the Redis maintenance events system to handle two new cluster failover events: FAILING_OVER and FAILED_OVER. These events complement the existing migration events (MIGRATING/MIGRATED) by providing handling for cluster node failover scenarios.

Key changes:

• Added two new event classes: NodeFailingOverEvent and NodeFailedOverEvent
• Integrated failover event handling into the existing maintenance event system using the same timeout relaxation mechanism as migration events
• Added comprehensive test coverage for the new events including integration tests

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
redis/maintenance_events.py	Added new failover event classes and integrated them into the event handler system
tests/test_maintenance_events.py	Added unit tests for the new event classes and updated existing tests to use the generalized event handling methods
tests/test_maintenance_events_handling.py	Added integration tests simulating failover events in the mock Redis communication layer

Comments suppressed due to low confidence (1)

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