Add Azure Managed Grafana Integration

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

Aspire does not currently have an Azure Managed Grafana integration. There is a [demo app](https://github.com/dotnet/aspire-samples/tree/main/samples/Metrics) for local Grafana development, but an Azure Managed Grafana integration would offer some substantial benefits:

* **Identity configuration**: There's a good security story around Aspire setting only the permissions required by Grafana. It's too easy to grant excessive permissions with Azure Managed Grafana manually.
* **Dashboard configuration**: Aspire's intimate understanding of the project can allow it to auto-include dashboards based on the AppHost's resources.

There's a good story with Azure Managed Grafana owing to Aspire's knowledge of the project's resources, and how Aspire can configure the Grafana instance for the user.

### Describe the solution you'd like

An Azure Managed Grafana integration would best serve the community by offering:
* Identity configuration that gives Azure Managed Grafana the minimum permissions necessary.
* Auto-installed dashboards. These dashboards already exist and are configured for Azure Monitor, though a bit scattered.
* See here for Grafana's incomplete list: https://grafana.com/orgs/azure/dashboards
* More dashboards are (for reasons unclear) listed under Azure Cosmos DB in the Grafana library. For example, here's the [Azure Open AI dashboard](https://grafana.com/grafana/dashboards/22552-azure-openai/).

### Additional context

_No response_