port the potd kded to kconfigwatcher + lazy init consumer/engine

it's easier on the eyes and also works properly... because of how configs can cascade across multiple directories the previous fixed path lookup wasn't all that correct. e.g. initially no file would be found at all, and when found it may not actually be the one in the user's home but e.g. in /etc/xdg

it also removes the unnecessary inotify instance the QFSW allocated as we now have no file system watch at all. this in turn reduces the excess stress plasma puts on the inotify instance cap

also reduce memory footprint by lazy initializing the engine stuff until we actually know that potd is used