Replace rootston

Epic: https://source.puri.sm/Librem5/use-cases/issues/7

Phoc is more maintainable and more phone-specific than using rootston directly. Having it will open the way to close some stale but important issues.

• Checklist
• Build phoc .deb
• Wlroots 0.6.0 not packaged
• Phone Essentials List
• Blank screen on boot in quemu
• Crash on intel
• Allow to build with and without embedded wlroots
• Wlroots 0.6.0 not in our repos
• Phoc coredump (while sitting in gnome-contacts)
• segfault when launching donf-editor
• Crash in rendering
• crash on emacs startup
• Crash related to subsurfaces
• coredump from chatty group add in matrix #248