lib kokkos: Enable deterministic use of Random_XorShift*_Pool. Add support for lock-free and deterministic use of Random_XorShift*_Pool by giving state_idx selection and lock responsibility up to the application. Done by an overload of get_state() to take sate_idx as an argument that the appplication guarantees is concurrently unique and within the range of num_states that the application passed to init(). In other words, this allows the RNG state to be associated with some application specific index, rather than a runtime arbitrary thread ID, and thus the application can control which work is performed using which RNG in a deterministic manner, regardless of which thread performs the work.