Fix illegal memory access for textureless meshes

[STREM-hexagon]

Creating a dummy texture for textureless meshes the way it is done so far causes illegal memory accesses if num_vertices * num_views > 1920 * 1080. To avoid this, this PR allocates a vertex color array instead of a texture and uses broadcasting to correctly access the colors in the renderer.

[yuanknv]

Thanks for catching and fixing this, it looks good to me. We will include this fix in the next patch for release-3.2.