The override material of scene that support both Mesh and InstanceMesh meanwhile

[dayinji]

Is your feature request related to a problem? Please describe.

Yes, as document describes, material cannot be shared by Mesh and InstanceMesh. So when I set override material of scene, it would no work on one of Mesh and InstanceMesh.
I guess this is because the material will be compiled before rendering. Once a Mesh object is rendered first, the vertexShader of the material will not contain the code blocks required by InstanceMesh.
So, for example, when I render a scene contains Mesh and InstanceMesh, and use a BokehPass which required a override material to render a depth buffer, it will trigger a visual bug.

Describe the solution you'd like

1. Add an overriedMaterialForInstance property to Scene, and once the overrideMaterial is set, we clone it to overriedMaterialForInstance.
2. Inside the renderObjects function of WebGLRenderer. we override object's material based on whether it is instanceof Mesh or InstanceMesh.

If you think the solution I proposed is feasible, I am willing to submit a PR.

Describe alternatives you've considered

None.

Additional context

None.

[Mugen87]

Duplicate of #17701.