VNet Peering enhancements

[ninjarobot]

This PR closes #1073

The changes in this PR are as follows:

• VNet Peering enhancements.
• Vnet enforcement for VM encryption (work in progress)

I have read the contributing guidelines and have completed the following:

• Tested my code end-to-end against a live Azure subscription.
• Updated the documentation in the docs folder for the affected changes.
• Written unit tests against the modified code that I have made.
• Updated the release notes with a new entry for this PR.
• Checked the coding standards outlined in the contributions guide and ensured my code adheres to them.

If I haven't completed any of the tasks above, I include the reasons why here:
Work in progress

Below is a minimal example configuration that includes the new features, which can be used to deploy to Azure:

let vnet1 =
    vnet {
        name "vnet1"
        add_address_spaces [ "10.100.50.0/24"; "10.100.255.0/24" ]

        add_subnets
            [
                subnet {
                    name "net1-1"
                    prefix "10.100.50.0/28"
                }
                subnet {
                    name "GatewaySubnet"
                    prefix "10.100.255.0/24"
                }
            ]
    }

let vnetGateway =
    gateway {
        name "vnet1-gw"
        vnet vnet1
    }

let vnet2 =
    vnet {
        name "vnet2"

        add_peering (
            vnetPeering {
                remote_vnet vnet1
                direction OneWayToRemote
                access AccessOnly
                transit UseRemoteGateway
                do_not_verify_remote_gateways true
                peering_state PeeringState.Initiated
                peering_sync_level PeeringSyncLevel.RemoteNotInSync
                add_remote_address_space_prefixes [ "192.168.50.0/24" ]
                add_remote_vnet_address_space_prefixes [ "10.100.200.0/24" ]
                depends_on vnetGateway
            }
        )

        add_address_spaces [ "172.16.120.0/24" ]

        add_subnets
            [
                subnet {
                    name "net2-1"
                    prefix "172.16.120.0/28"
                }
            ]
    }
arm {
    location Location.EastUS
    add_resources [ vnet1; vnetGateway; vnet2 ]
}

[ninjarobot]

I converted this to a draft since it looks like it may not really be necessary.