WIP: [Android] Multicast backend

Summary: Add a Multicast (aka. mDNS, aka. Bonjour, aka avahi) backed to KDE Connect for Android

Many networks block KDE Connect's UDP broadcasts but work after manually adding the IP address. Many networks block UDP broadcasts but allow mDNS service discovery. This patch adds mDNS discovery to make KDE Connect more reliably able to autoconnect

Test Plan

Currently there is no pairing possible but you can see the device's mDNS broadcast by doing avahi-browse -ar and look for a line with kdeconnect