Remove the indirection previously used for the topology refiner
to separate C and C++ code. Instead retrieve the base level in
calling code and call opensubdiv API functions directly. This
avoids copying arrays of mesh indices and should reduce
function call overhead since index retrieval can now be inlined.
It also lets us remove a lot of boilerplate shim code.
The downside is increased need for WITH_OPENSUBDIV defines
in various parts of blenkernel, but I think that is required to avoid
the previous indirection and have the kernel deal with OpenSubdiv
more directly.
Pull Request: https://projects.blender.org/blender/blender/pulls/120825
5e46e3d28a