Tails

Test suite: adapt/add Gherkin scenarios for 1BigIUK.

No work on the steps have been done so far.

Refs: #15286

Test suite: implement missing steps for IUK scenarios.

Will-fix: #15286

Add UDFs for 4.x under the v2 URL format (refs: #15286)

The new Upgrader, that'll be shipped in 4.2, will start looking
for upgrades via the v2 API. Until something strictly newer
than 4.2 is built and tested, there won't be upgrades available
regardless of the initially installed version.

Test suite: prettify (refs: #15286)

… as suggested by anonym when he implemented this initially :)

WIP: Test suite: verify that previous SquashFS deltas are actually deleted (refs: #15286)

Test suite: salvage note about missing test (refs: #15286)

This brings back 2763439ddf07cf0fb4eec091a40135e7dda1a67f:
https://redmine.tails.boum.org/code/issues/15286#note-8

Test suite: move step where it belongs (refs: #15286)

This is about verifying that the upgrade was correctly applied,
not about the Unsafe Browser.

Add a crude script to generate IUKs for our test suite (refs: #15286)

Doing this by hand one more time now, and once again soon for IUK v2 +
overlayfs, was not particularly appealing.

Test suite: fix syntax (refs: #15286)

Test suite: fix Gherkin (refs: #15286)

Given the test UDFs we're using, an initially installed 2.0~test
will be upgraded to 2.2~test.

Test suite: ensure our test IUKs don't break the next boot (refs: #15286)

Test suite: update reference image (refs: #15286)

Test suite: avoid robustness step introducing fragility (refs: #15286)

I've seen cases when the ESC key stroke in "all notifications have disappeared"
closes the very dialog that we'll be looking for in the next step
("I am proposed to install an incremental upgrade to…"). I suspect
this never happened before because the Upgrader took longer to start,
so optimizing it introduced this race condition.

In these scenarios, I doubt that closing notifications is important: the
aforementioned zenity dialog is always displayed in the center of the screen and
there's little change a notification hides it.