replace interrupts tech with cli module

this either cats /proc/interrupts (on linux) or calls vmstat (on freebsd). vmstat is always available on freebsd, consequently this kcm doesn't have any associated find_package boilerplate

unlike some other kcm replacement this doesn't really shrink the code base on its own but will eventually if we can get rid of all the other base modules as well, such that we can remove the entire qwidget view building code