Add test for the instance param (geometry shader)

Test/hlsl.instance.geom

@@ -0,0 +1,17 @@
+struct VertexShaderOutput
+{
+    float4 m_position : SV_POSITION;
+    float4 m_color    : COLOR0;     
+};
+
+[maxvertexcount(3)]
+[instance(5)]
+void GeometryShader(triangle VertexShaderOutput input[3], inout TriangleStream<VertexShaderOutput> output, uint id : SV_GSInstanceID)
+{
+    [loop]
+    for (int i = 0; i < 3; ++i)
+    {
+        output.Append(input[i]);
+    }
+    output.RestartStrip();
+}