[BUG] Reuse C API parameter structs in C++

[ajit283]

We should use the C parameters structs in C++, e.g. using cuvsCagraExtendParams instead of cuvs::neighbors::cagra::extend_params, since having parallel objects like this increases the maintenance burden. An example where this is already done:

cuvs/cpp/include/cuvs/distance/distance.hpp

Line 27 in 72154b0

using DistanceType = cuvsDistanceType;