Brute force integrate PSD not compatible with NonUniformLineScan

[sannant]

I suggest to create a copy of the container that interpolates all the linescans. At least as a shortterm soluion.

def _interpolate_nonuniform(self, nb_interpolate=5):
    topographies = []
    for t in self._topographies:
        if not t.is_uniform:
            t = t.to_uniform(nb_interpolate=nb_interpolate)
        
        topographies.append(t)
    return SurfaceContainer(topographies=topographies)

The reason I create the whole container is that we need to know the pixel size of the inerpolated PSD to compute the weighting factors before actually computing the PSD.