Public Preview: Query-based metric alerts in Azure Monitor

Azure Monitor metric alerts now support all Azure metrics - including platform, Prometheus, and custom metrics - giving you complete coverage for your monitoring needs. In addition, metric alerts now offer powerful query capabilities with [PromQL](https://prometheus.io/docs/prometheus/latest/querying/basics/), the industry-standard query language, on Prometheus metrics, OTel-based VM performance counters, and other OTel custom metrics ingested into Azure Monitor Workspace (AMW). Key Capabilities: * **PromQL-based conditions:** Leverage the full power of PromQL for sophisticated metric selection, aggregation, and transformation. * **Flexible scoping:** Choose between resource-centric alerts for granular RBAC or workspace-centric alerts for cross-resource visibility. * **Managed Identity support:** Securely authorize queries using Azure Managed Identity. * **Customizable notifications:** Add dynamic custom properties and custom email subjects for faster triage and context-rich alerting. With query-based metric alerts, you can detect complex patterns, reduce alert noise, and reuse existing community-based Prometheus alert logic - all while maintaining a unified monitoring experience in Azure. This feature empowers teams to proactively manage performance and reliability at scale, without sacrificing flexibility or security.