LibGL+LibSoftGPU: Implement normalization of normals

* LibGL now supports the `GL_NORMALIZE` capability
* LibSoftGPU transforms and normalizes the vertices' normals

Normals are heavily used in texture coordinate generation, to be
implemented in a future commit.

Userland/Libraries/LibGL/SoftwareGLContext.h

@@ -206,6 +206,7 @@ private:
     GLclampf m_alpha_test_ref_value = 0;
 
     bool m_dither_enabled { true };
+    bool m_normalize { false };
 
     // Stencil configuration
     bool m_stencil_test_enabled { false };