Sparse mat-vec: Remove optimizations for multiple right-hand sides by default

[mhoemmen]

Or at least have a CMake option to disable them. A large customer really does not care about multiple right-hand sides, and is starting to hit the 4GB linker limit for debug builds.

@crtrott already has a macro for this, so this should just be a matter of adding a CMake option to define or undefine the macro, then testing with both options.

[mhoemmen]

See lines 932-1021 of kokkos-kernels/src/impl/Kokkos_Sparse_impl_spmv.hpp. I would like to make this a separate option from KOKKOS_FAST_COMPILE. Special cases (e.g., alpha and beta) for single-vector sparse matrix-vector multiply still need to be fast. I just want to avoid building all the multiple-right-hand side cases.