Update AI Gateway monitoring to use the current OpenTelemetry configuration #9

Problem

The sample currently configures telemetryExporters with kind: applicationInsights and an Application Insights connection string. The current AI Gateway monitoring experience expects the native OTLP/OpenTelemetry configuration, so the portal does not reliably recognize this legacy exporter as monitoring-enabled.

Missing configuration

• Register the Microsoft.Monitor resource provider.
• Set AzureMonitorWorkspaceIngestionMode: Enabled on the workspace-based Application Insights resource.
• Wait for Application Insights to generate its managed DCR/DCE and OTLP endpoints.
• Configure the exporter with kind: OpenTelemetry, the Application Insights resource ID, metrics/logs/traces OTLP endpoints, and managed-identity audience https://monitor.azure.com.
• Assign the AI Gateway system-assigned identity the Monitoring Metrics Publisher role (3913510d-42f4-4e42-8a64-420c390055eb) at the generated DCR scope.
• Account for the deny assignment on the generated managed resource group: a nested ARM/Bicep role assignment is blocked, while a direct role-assignment PUT from an azd post-provision hook works.
• Document that exporter kind is immutable, requiring delete/recreate when migrating an existing legacy exporter.

Current preview behavior

The service currently persists metrics and logs endpoints but may omit a supplied tracesEndpoint from exporter GET responses. Metrics and logs are sufficient for the portal dashboard eligibility check.