GPU: Replace GPUMaterialVolumeGrid by GPUMaterialAttribute

This is to make the codegen and shading nodes object type agnostic. This
is essential for flexibility of the engine to use the nodetree as it see
fits.

The essential volume attributes struct properties are moved to the
`GPUMaterialAttribute` which see its final input name set on creation.

The binding process is centralized into `draw_volume.cc` to avoid
duplicating the code between multiple engines. It mimics the hair attributes
process.

Volume object grid transforms and other per object uniforms are packed into
one UBO per object. The grid transform is now based on object which simplify
the matrix preparations.

This also gets rid of the double transforms and use object info orco factors
for volume objects.

Tagging @brecht because he did the initial implementation of Volume Grids.

source/blender/draw/intern/draw_manager.h

@@ -527,6 +527,8 @@ typedef struct DRWData {
   struct GPUUniformBuf **obinfos_ubo;
   struct GHash *obattrs_ubo_pool;
   uint ubo_len;
+  /** Per draw-call volume object data. */
+  void *volume_grids_ubos; /* VolumeUniformBufPool */
   /** List of smoke textures to free after drawing. */
   ListBase smoke_textures;
   /** Texture pool to reuse temp texture across engines. */