core: drop support for old per-distro configuration files for console, hostname,...

core: drop support for old per-distro configuration files for console, hostname, locale, timezone

This simplifies the upstream system code quite a bit. If downstream distributions want to maintain compatibility with their old configuration files, they are welcome to do so, but need to maintain this as patches downstream. The burden needs to be on the distributions to maintain differences here. Our suggestion however is to just convert the old configuration files on upgrade, as multiple distributions already do.