Rename VkFunctorDrawable->VkInteropFunctorDrawable

The Vulkan functor is currently doing interop, calling into the real
OpenGL functor. We will be adding a real, non-interop Vulkan functor
soon. In order to enable that, this patch renames the existing
VkFunctorDrawable to VkInteropFunctorDrawable. That allows us to use the
name VkFunctorDrawable for the real functor.

Test: This is a simple rename. Existing unit tests should work.

BUG=115613038

Change-Id: I427ad4d17ee92c3832e7bace55450b41a036f557