This is to address PR 2 described in #1118 (comment). Have copied the corresponding notes below:

1. Add each new (simple) def _X_sliding_dot_product to sdp.py (i.e., _convolve_sliding_dot_product, _oaconvolve_sliding_dot_product, _pocketfft_sliding_dot_product
2. Add unit tests that demonstrate that each _X_sliding_dot_product matches the results of naive_rolling_window_dot_product