Add RenderingServer.get_video_adapter_type() method

This can be used to distinguish between integrated, dedicated, virtual
and software-emulated GPUs. This in turn can be used to automatically
adjust graphics settings, or warn users about features that may run
slowly on their hardware.

servers/rendering_server.h

@@ -1473,6 +1473,7 @@ public:
 	virtual uint64_t get_rendering_info(RenderingInfo p_info) = 0;
 	virtual String get_video_adapter_name() const = 0;
 	virtual String get_video_adapter_vendor() const = 0;
+	virtual RenderingDevice::DeviceType get_video_adapter_type() const = 0;
 
 	struct FrameProfileArea {
 		String name;