[Feature] Managed Mesh Versioning upgrade and maintenance

Before Managed Mesh Upgrade and Version Management, AKS customers using Istio service mesh faced complex, multi-step upgrade procedures that required installing parallel control planes with different revisions, manually coordinating namespace relabeling from `istio-injection=enabled` to `istio.io/rev=canary`, restarting all workloads to trigger sidecar re-injection, and managing manual cleanup of old control plane components. Security patching required weeks of coordination across teams, creating extended vulnerability windows. Teams relied on spreadsheets and custom scripts to coordinate maintenance windows, with no centralized view of upgrade status across clusters. Rollback procedures required manual gateway reinstallation and complex revision tag management, risking service disruption.

Now, AKS customers can automate mesh lifecycle operations with policy-driven upgrades that handle canary orchestration seamlessly, integration with reusable maintenance configurations for predictable scheduling, and automated rollback capabilities with health-based triggers to achieve enterprise-grade operational maturity at scale while eliminating the operational overhead of manual revision management.