Set proxy on Windows VMs while provisioning

Task-number: QTQAINFRA-1669
Change-Id: Ia6b5b668051642a3729d7c7c83c69d8797045847
Reviewed-by: Heikki Halmet <heikki.halmet@qt.io>

coin/provisioning/common/windows/helpers.ps1

@@ -144,3 +144,11 @@ Function Execute-Command
         exit 1
     }
 }
+
+function isProxyEnabled {
+    return (Get-ItemProperty -Path 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings').proxyEnable
+}
+
+function getProxy {
+    return (Get-ItemProperty -Path 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings').proxyServer
+}