Add int attributes interpolation support for GPU subdivision.
Ensure cached shaders match their intended defines.
(The defines parameter was ignored when requesting a second time the same shader with different defines)
De-duplicate the extract_attr_init code for subdiv/non-subdiv.
Reviewed By: jbakker, fclem
Maniphest Tasks: T102076
Differential Revision: https://developer.blender.org/D16420
2a53e0f437