[ui] Viewer3D: introduce SphericalHarmonics shader + display mode

Add experimental render mode to display model normals or shading based on spherical harmonics coefficients

meshroom/ui/qml/Viewer3D/Materials/shaders/SphericalHarmonics.vert

@@ -0,0 +1,16 @@
+#version 330 core
+
+in vec3 vertexPosition;
+in vec3 vertexNormal;
+
+out vec3 normal;
+
+uniform mat4 modelView;
+uniform mat3 modelViewNormal;
+uniform mat4 mvp;
+
+void main()
+{
+    normal = vertexNormal;
+    gl_Position = mvp * vec4( vertexPosition, 1.0 );
+}