webgpu: Fix occlusion culling incorrect behavior
Extended the number of mipmaps up to 1x1 which may be needed for very large objects (the shader was reading in undefined mipmap level before this fix, leading to undefined behavior and incorrect culling on some drivers). Proper redefinition of the number of mipmaps of the hierarchical z buffer texture view in the cullin pass of the occlusion culler.
Last commit only is relevant.
Edited by Tom Clabault