Persist a random seed across boots

Originally created by @bertagaz on #11897 (Redmine)

Given I boot Tails from a USB stick
Then I want to have good entropy from a random seed, regardless of whether I have persistence enabled or not

Blueprint: https://tails.boum.org/blueprint/randomness_seeding

Feature Branch: feature/11897-improve-random-seed-file, installer:segfault/feature/11897-Create-install-ramdom-seed