Add simple evaluation method to TFCSEnergyInterpolationPiecewiseLinear

This MR adds a simple evaluate method in the FastCaloSim TFCSEnergyInterpolationPiecewiseLinear class. Allows tho evaluate interpolation at arbitrary Ekin. If the lookup is below (above) the minimum (maximum) interpolation value, will return minimum (maximum) evaluation. No extrapolation beyond those points is performed. MR is required for !50562 (merged)