Allow customization of the WebRTC UDP ports range.
In some constrained environments where a firewall blocks UDP network traffic excepted on a specific port range, this settings can be used to give hints to the WebRTC backend regarding which ports to allocate. The format is min-port:max-port, so for instance 20000:30000. The default empty string value means the OS will use no hints from the WebRTC backend. Using 0 for one of the values is allowed and means the value is unspecified.
Set webrtcUdpPortsRange property.