PowerShell direct support for Hyper-V

_This issue was originally opened by @Sarafian as hashicorp/packer#6359. It was migrated here as a result of the [Packer plugin split](https://github.com/hashicorp/packer/issues/8610#issuecomment-770034737). The original body of the issue is below._

Microsoft released recently this concept where PowerShell can connect to a VM just by using the VMName without the necessity to use credentials nor the target OS having a full network stack configured. This is known as [PowerShell Direct](https://blogs.technet.microsoft.com/virtualization/2015/05/14/powershell-direct-running-powershell-inside-a-virtual-machine-from-the-hyper-v-host/).

This could be very useful when working with Hyper-V network configuration as `internal`. For the current provisioner to work, somehow the network stack needs to be fully configured, then it's IP it needs to become know and then the packer client can provision.

With PowerShell direct this won't be necessary any longer.

There is a similar [request](https://github.com/hashicorp/vagrant/issues/8810) for the vagrant provisioners. There a new type of provisioner is being discussed.