[SMS App] Handle addresses for multitarget messages

Summary

Upgrade the SMS App to handle multitarget addresses in the "addresses" field of a message and drop usage of the "address" field

Also note that this has all the commits from https://invent.kde.org/kde/kdeconnect-kde/merge_requests/97, but I will rebase those away once that patch is landed

Bonus: Image composition for multitarget conversations:

• Two Participants:
• Three Participants:
• Four Participants:

Test Plan

• Apply Android-side patch https://invent.kde.org/kde/kdeconnect-android/merge_requests/80
• Launch SMS App
• Notice that you can see all the recipients of multitarget messages. (Replying still not supported, but might get implemented as part of fixing replying to single-target messages)