Remove uses of ScopedCudaStackSize

Since we have (hopefully) gotten rid of all unbounded recursion and
calls to function pointers or virtual methods, the CUDA compiler should
be able to statically determine the size of the stack needed. Thus, we
shouldn't need `ScopedCudaStackSize` at all.

However, there is one odd case where using it seems to be necessary. It
is unclear why, but that is an issue for another day.