Generics support

Supporting Generics in Wing could be used to provide useful errors between preflight and inflight code:

bring cloud;

struct A {
  field1: str;
  field2: num;
}

let bucket = new cloud.Bucket();
let queue = new cloud.Queue<A>();

let processor = new cloud.Function((event: Array<A>) ~> {
    print("Received a batch where the first message is ${event[0]}");
});
queue.onMessage(processor);
bucket.onUpload(processor); // ERROR: Bucket.onUpload expects an argument of type Function<BucketUploadEvent> but received Function<Array<A>>

let notifier: cloud.Function<cloud.BucketUploadEvent> = new cloud.Function((event: cloud.BucketUploadEvent) ~> {
    print("File ${event.file} was uploaded on {event.date}");
});
bucket.onUpload(notifier);
queue.onMessage(notifier); // ERROR: Queue.onMessage expects an argument of type Function<Array<A>> but received Function<BucketUploadEvent>

To support JSII interoperability, I'd propose that during compilation we might be able to perform type erasure like Java that convert type paramters like T into any, and add JSII metadata that details any of the erased type information.

The issue names no files, tests, or entry points. Start by reviewing the compiler's type-checking path and JSII interoperability design; done should include generic type checking between preflight and inflight code and metadata for erased type information.