Fix T75964: changing object's viewport display color does not update cycles
Fix T75964: changing object's viewport display color does not update cycles

Caused by rB00466e756e33.

While that commit sounds logical, Cycles uses is_updated_transform() to
detect updates.

Now introduce is_updated_shading() and use that on top.

Maniphest Tasks: T75964

Differential Revision: https://developer.blender.org/D7493

tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird