Write CDK to build dev EC2 instance for deploying Sleeper from

[patchwork01]

gchq#37

[patchwork01]

When I deployed sleeper in a VPC with a single public subnet, the system test wouldn't run because it uses an ECS task with the awsvpc network mode. It failed with this stopped reason:

ResourceInitializationError: unable to pull secrets or registry auth: execution resource retrieval failed: unable to retrieve ecr registry auth: service call has been retried 3 time(s): RequestError: send request failed caused by: Post https://api.ecr.eu-west-2.amazonaws.com/: dial tcp 52.94.57.33:443: i/o timeout

See this article:

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-networking-awsvpc.html

When hosting tasks that use the awsvpc network mode on Amazon EC2 Linux instances, your task ENIs aren't given public IP addresses. To access the internet, tasks must be launched in a private subnet that's configured to use a NAT gateway. For more information, see NAT gateways in the Amazon VPC User Guide. Inbound network access must be from within a VPC that uses the private IP address or routed through a load balancer from within the VPC. Tasks that are launched within public subnets do not have access to the internet.

Maybe it would work with an endpoint for ECR, but I just set up a private subnet with a NAT and that fixed it.