Support expand tokens for querying a resource

Certain resources like blueprints and template specs use an expand token in the GET URI to return extra information that is typically more expensive to retrieve. There is no way to express this for bicep resources (or ARM templates). I wonder if in the ARM layer it should be an extra argument on the `reference()` function.

Discovered through #2378

Start with the behavior described in #2378 and trace how the ARM layer handles GET URIs and the `reference()` function. Compare expand-token queries for blueprints and template specs with bicep resources and ARM templates; done means the intended syntax and behavior are defined for both resource forms.

Written by the indexing model from the issue text.