(#19877) OpenWrt Support

This pull request includes preliminary support for OpenWrt as a supported platform. OpenWrt is an embedded linux distro, and these commits enable its specific init scripts (service provider) and package management (opkg)

I left ab4e421 as a separate commit if you need to cherry pick it, as I thought it might be controversial. I committed it as I believe that automatic package list downloading is what most puppet administrators would expect (least surprise).