feat(ec2): add dual stack vpc support (#28480)

Adds parameter to configure a dual stack vpc, `vpcProtocol: ec2.VpcProtocol.DUAL_STACK`.

By default a dual stack vpc will:

- Create an Amazon provided IPv6 CIDR block (/56) and associate it to the VPC.
- Assign a portion of the block to each of the subnets (/64)
- Enable autoassigning an IPv6 address for each subnet
- **Disable autoassigning public IPv4 addresses** for each subnet
- Create an Egress Only Internet Gateway for private subnets
- Configure IPv6 routes for IGWs and EIGWs

Addresses #894.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk-testing/framework-integ/test/aws-ec2/test/integ.vpc-dual-stack-ec2.assets/web-server.py

@@ -0,0 +1,40 @@
+from http.server import SimpleHTTPRequestHandler
+import urllib.request
+import json
+
+class MyRequestHandler(SimpleHTTPRequestHandler):
+    def do_GET(self):
+        if self.path == '/':
+            self.send_response(200)
+            self.send_header('Content-type', 'application/json')
+            self.end_headers()
+
+            try:
+                # IPv4 request
+                response = urllib.request.urlopen('http://ipv4.google.com')
+                status_code = response.getcode()  
+                if (status_code != 200):
+                  raise Exception(f"Received a non-successful status code: {status_code}")
+
+                # IPv6 request
+                response = urllib.request.urlopen('http://ipv6.google.com')
+                status_code = response.getcode()  
+                if (status_code != 200):
+                  raise Exception(f"Received a non-successful status code: {status_code}")
+
+                json_response = { 
+                    "status": status_code
+                    }
+
+                self.wfile.write(json.dumps(json_response).encode('utf-8'))
+            except Exception as e:
+                self.wfile.write(bytes(f"Error: {str(e)}", 'utf-8'))
+            return
+        else:
+            super().do_GET()
+
+if __name__ == '__main__':
+    from http.server import HTTPServer
+    server = HTTPServer(('0.0.0.0', 8000), MyRequestHandler)
+    print('Server started on http://0.0.0.0:8000')
+    server.serve_forever()