Assembly references used by anonymous types are not added to the set of used assembly references.

```
        [ConditionalFact(typeof(NoUsedAssembliesValidation))] // PROTOTYPE(RefStructInterfaces): Follow up on used assemblies validation failure. Could be an artifact of https://github.com/dotnet/roslyn/issues/72945.
        [WorkItem("https://github.com/dotnet/roslyn/issues/72945")]
        public void AnonymousTypeMember_02()
```