Farmer support for route server

[Huaxinli123]

This PR closes #

The changes in this PR are as follows:

• Adding support for route servers
• Support adding bgp connections and vnet during creation of route server

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

• [x] Tested my code end-to-end against a live Azure subscription.
• [x] Updated the documentation in the docs folder for the affected changes.
• [x] Written unit tests against the modified code that I have made.
• [x] Updated the release notes with a new entry for this PR.
• [x] 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:

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

#r "nuget:Farmer"

open Farmer
open Farmer.Builders

arm {
    location Location.EastUS
    add_resources
        [
            vnet {
                name "test-vnet"
                add_address_spaces [ "10.0.0.0/16" ]
            }
            routeServer {
                name "my-route-server"
                sku RouteServer.Sku.Standard
                subnetPrefix "10.0.12.0/24"
                linkToVnet (virtualNetworks.resourceId "test-vnet")

                add_BGPConnections [
                    routeServerBGPConnection {
                        connectionName "my-bgp-conn"
                        peerIp "10.0.1.85"
                        peerAsn 65000
                    }
                ]
            }
        ]
}

[ninjarobot]

Thanks @Huaxinli123, this is included in 1.7.23 and available on nuget.