MetGrid GPU Fix

[AMLattanzi]

The construction of the base state with MetGrid had a foundational issue when on the GPU. Specifically, the use of DeviceVectors to do column-wise operations will not work on the GPU since multiple threads will try to access that vector at the same time, causing a race condition. We now eliminate the calc_rho_p routine and directly interact with the Newton_Raphson iterator by integrating from k = [1 kmax], where we need only k-1 and k values.