CPAlgorithms: save weight systematics separately in the SysListDumperAlg

Feature requested by @alheld: recording the names of the weight-based systematics separately, so downstream histogramming frameworks can more efficiently produce the histograms (compute observable once, fill N times; instead of doing N times the computation+filling).

Here we schedule another instance of the CP::SysListDumperAlg, but this time equipped with a regexp filter to retain only systematics associated to weights.