Get the list of persistence presets from the Tails being tested.

... instead of maintaining a static list that often gets out-dated,
and makes it impossible to run usb_install.feature with an --old-iso
that has a different set of presets. That's still not possible, but
this is one step in that direction.
Actually test permissions of link-type persistent directories.

... such as the one for the "dot files" persistence preset. The
removed code was supposed to do that, but was bugged (we didn't loop
over the `all_persistent_dirs` we crafted for that purpose).
Improve variable name.
Make it possible to use an old iso with different persistence presets.

... by only checking that the persistence presets that were available
when installing Tails from the old iso are enabled. Any new presets in
the "current" iso are not checked.
We should not ignore missing persistent source directories.

That should imply that something has gone very wrong. I'm not sure why
we've been ignoring them (certainly it would deserve a comment!) but I
can imagine there was some thought about the "old iso with fewer
presets than the current iso" situation that was just solved, but that
wouldn't be enough for some of the other checks.
Check access rights of all persistent source directories.

We don't want the persistent system directories to be too restrictive
nor to lax (at least the current ones).
Improve some steps' names grammatically and descriptively.
Slightly simplify code, and remove magic number.

This is "slightly" more straigh-forward, and not having to bump the
number is nice, especially now when the list of presets is dynamically
fetched from the Tails system being tested. From now on there should
be no need to add support for new persistence presets in the test
suite without breaking it, and they will benefit from the very basic
and general testing we do of each of them.
Verify that all available presets were enabled.

Mostly to verify that the crazy keyboard commands used to check them
in t-p-s works.
Bump test timeouts a bit.

Sometimes, at least in my testing environment, the *icons* in the GNOME
applications menu take longer than 10 seconds to appear, presumably because some
cache is being initialized.
Update patch to include all Intel CPU microcodes (Closes: #8189).

First, make it actually apply on current /etc/default/intel-microcode.

Second, keep using IUCODE_TOOL_SCANCPUS=no, as we still want to include all
microcodes, not only the one(s) for the build machine's CPU.

Third, use forced early mode for IUCODE_TOOL_INITRAMFS:

  * We can't use non-early initramfs mode anymore, since support for it has
    been removed.
  * We could not use "early" mode with the previous version of the
    intel-microcode packaging, since it only supported building on Intel CPU.
  * Quoting debian/changelog: "early" mode now allows a "non-Intel box to
    generate an early initramfs with microcode for an Intel box", and "on auto
    mode, do nothing in a non-intel box. In forced "early" mode, attempt to run
    iucode-tool".

So, this introduces a change in behaviour, but that's the best supported one,
the most robust one, and the one we wanted to use previously but could not.
Merge branch 'bugfix/8189-intel-microcode-v3' into stable
Merge branch 'bugfix/8189-intel-microcode-v3' into experimental
Merge branch 'test/8091-improve-old-iso-testing' into experimental

Conflicts:
	features/step_definitions/usb.rb
Merge branch 'test/8140-more-robust-apps-menu' into experimental
Merge branch 'stable' into test/8140-more-robust-apps-menu
Merge branch 'test/8140-more-robust-apps-menu' into experimental
Fix typo.
Merge branch 'bugfix/7951-refactor-chroot-browsers' into experimental