0031096: Visualization, TKOpenGl - support metallic-roughness texture mapping

OpenGl_ShaderManager - metallic-roughness, emissive, occlusion
and normal texture maps are now supported by PBR.
Emissive, occlusion and normal texture maps are now supported by Phong shading model.
Path-Tracing now handles metallic-roughness and emissive texture maps.

Graphic3d_TextureUnit enumeration has been extended by
new values corresponding to supported texture maps.

OpenGl_TextureSet and OpenGl_ShaderProgram have been extended with
bitmask Graphic3d_TextureSetBits identifying texture slots read from GLSL Program
and slots defined within Texture Set to avoid undefined behavior by binding mock textures.

OpenGl_TextureSet now duplicates texture unit information to handle
textures shared across multiple slots (like Occlusion [R] + Metallic-Roughness [GB]).

OpenGl_Context::BindTextures() has been extended with active GLSL program paramter
to set mock textures to texture units used by program but undefined by texture set.
OpenGl_Workspace::ApplyAspects() has been extended with parameter to avoid bining texture set.

src/XCAFPrs/XCAFPrs_Texture.cxx

@@ -31,6 +31,8 @@ XCAFPrs_Texture::XCAFPrs_Texture (const Image_Texture& theImageSource,
     myTexId = myImageSource.TextureId();
   }
   myParams->SetTextureUnit (theUnit);
+  myIsColorMap = theUnit == Graphic3d_TextureUnit_BaseColor
+              || theUnit == Graphic3d_TextureUnit_Emissive;
 }
 
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