Create and assign a static IP when using GCE

Thanks to @richardcase for reporting this - I don't know if it's new behaviour or if we never noticed it before, but GCE VMs now get an ephemeral IP instead of a stable one.

I've updated the docs with instructions on what to do to work around this, but it'd be a far better user experience, if the provisioning library did this for customers.

The IPs cost 2.88USD / mo, unless they are orphaned in which case the cost increases, so it'd be important to track it and remove it when the VM was removed.

I also did some research into whether a stable DNS entry was created (like you get with EC2 VMs on AWS, but there isn't one)

https://docs.inlets.dev/reference/inletsctl/#example-usage-with-aws-ec2-temporary-credentials