MDMC should interpolate computational results to the experimental

**Description of the error**
There seems to be some odd ways in which MDMC matches the experimental results to the computational ones.

There seems to be some requirements on the time_step and traj_step so that they match the experimental results. MDMC also seems to interpolate the experimental results to computational ones when FFT is used? This is probably why FoM is different in #1648 because the points that are being compared are different and depend on the quality of the interpolation of the experimental results, which may not be accurate if experimental results are sparse.

This seems more complicated than it ever needed to be. Why don't we just interpolate the computational results to match the experimental. This means there would be no requirements on the time_step, traj_step, or unit cell size, and a better interpolation of the computed results can be made easily by the user by decreasing the time_step or traj_step and increasing the unit cell size.