Support variables in Azure Monitor queries

[asosMikeGore]

The current plugin doesn't appear to allow you to parameterise the resource group & resource names. I'd like to do this based on an environment convention e.g.

ResourceNamePrefix-$Environment

While I can enter the details and Grafana appears based on error message to transform the parameter names, I can't enter a timegrain in the query or get to a point where I can successfully get a query parameterised this way to show up in a graph.

I'd rather not have to build a dashboard per-environment if at all possible. While we could query the information from Application Insights using variables, I'd rather query the metrics directly as they are available faster from the metric store than they are Application Insights.