Switch to test set patterns

Switch from accepting a single regex for matching test sets, to accepting "set patterns" - a set of regexes joined/modified by logical operators. This concerns both "kpet run" and "kpet test list" commands.

This allows specifying things like "kt0 & fs" for kt0 filesystem tests, or "kt1 & !kt0" for tests in kt1, which are not in kt0, and so on.