Watching for PRW that has already been applied

In DAOD_PHYSLITE, we already have PRW applied at the derivation stage. If tools set it up to run, it'll try to add a decoration -- but the one that was added in the derivation is there and is const (since it was in the file), so the code crashes. This adds a warning and early return in such cases. I'm not explicitly checking for const decorations, just for decorations that would have the same name as the ones to be added.