Please describe the feature you'd like to see added.

From #27446 (comment):

This brings up a related issue in that we can't have multiple signets in the same base datadir. All signets use the signet datadir, so any change of parameter may result in a bad chainstate for that signet node.

I think we should instead look at implementing a more robust multiple signet solution that allows for multiple configurable consensus rules in a clean and simple way since clearly that's desired. Ideally we would have a single parameter that contains all of the rules being configured rather than having multiple for each rule. We should also make datadirs specific to each set of rules, ideally in a deterministic way.