Adjust infrastructure and CI for USB images

Originally created by @Anonymous on #15993 (Redmine)

Adjust CI wrt. more outputs from the build jobs => more inputs for the test suite and reproducibility tests

This includes at least:
- store .img* artifacts too when building
- copy .img* artifacts too to other jobs that need them
- garbage-collect .img* too
- symlink duplicate .img* too
- Deal with increased disk space requirements on Jenkins and in the ISO archive
- probably more stuff that we’ll discover along the way
- post-release bugfixing

This work is supposed to be equally shared by groente and intrigeri.

Parent Task: tails#15292 (closed)

Subtasks

Edited May 15, 2020 by Anonymous