CPAlgorithms: enable systematics filtering in config blocks
The systematics regexp filtering option is exposed in the relevant config block, which also makes it accessible to the YAML config. One can then write:
CommonServices:
filterSystematics: ".*(JER|PRW).*?"
to run only those systematics that contain "JER" or "PRW" (or are the nominal variation, represented by the empty string). Or instead
CommonServices:
filterSystematics: "(?:(?!JER|PRW).)*"
to veto any systematics that contain "JER" or "PRW" (i.e. run everything else, including nominal).