[cdk] Allow users to easily consume CDK properties and Constructs from a Pulumi context

[pgavlin]

In order to provide an easy-to-use experience for the CDK bridge, we need to allow users to easily consume CDK properties and Constructs from a Pulumi context. While exactly how we export values from the CDK context is in question, I believe that we can look to the implementation of resolve in CDK to inform how we project exported values. I am reasonably confident that we can bridge properties that contain tokens as Outputs, and bridge Constructs as either ComponentResources (for L2+ constructs) or CustomResources (for L1 constructs). Bridging L2+ constructs will require that we walk the Construct tree and register a ComponentResource per L2+ construct–something that we probably want to do anyway for display purposes. We may be able to reuse work from #1 as part of this process.