Consider upgrading to current live-boot

Originally created by @intrigeri on #15477 (Redmine)

As of Tails 4.6, we’re using Stretch’s live-boot 1:20170112.

Upgrading is not trivial:

The changes brought by https://bugs.debian.org/886328 (“use /run/live instead of /lib/live/mount”) affect all kinds of stuff such as memory erasure, live-persist, AppArmor, and more.
See the initial porting attempt, reverted in f365b9bf

Edited May 19, 2020 by intrigeri

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information