interpolate waveform instead of psd
Currently we're using the LAL FrequencySeries data object internally, which only supports linear frequency spacing. This forces PSDs to be interpolated to a fixed frequency array to be compatible with the returned waveforms. If instead we punt on using the FrequencySeries internally, we can instead just interpolate the returned waveform to the PSD frequency array we're using.
This will require re-writing the SNR calculation function.