Generator: Fix IPageable + missing DynamicValues type for azureiotcentral

[daviburg]

The azureiotcentral connector fails code generation with two issues:

1. IPageable mismatch (same root cause as Generator: Fix IPageable interface mismatch for azuread connector #135):
   CS0535: DeviceGroupCollection does not implement interface member IPageable.Value

2. Missing DynamicValues attribute type:
   CS0246: The type or namespace name DynamicValues could not be found
   The generated client methods reference [DynamicValues(...)] but the attribute is not imported in the generated files usings.

Connector: azureiotcentral (Azure IoT Central)
Auth: AAD OAuth
Priority: Medium

Related to #7.