Apply greeter-buster-blocking-tails-unblock-network.diff to the Greeter files now shipped here (refs: #16912)

Merge branch 'bugfix/16941-torbrowser-launcher-0.3.2+force-all-tests' into feature/16912-move-greeter-to-main-git-repo

Merge remote-tracking branch 'origin/devel' into bugfix/16941-torbrowser-launcher-0.3.2+force-all-tests

Merge remote-tracking branch 'origin/bugfix/16601-fix-translations' into stable (Fix-committed: #16601)

I.e. it'll be built from the stable branch: testing & devel are now
based on Buster. This would be a special bugfix release as it would
include the upgrade to Tor Browser 9.0 (Firefox 68); we've already
done this sort of things and it went well.

Currently translated at 33.3% (6 of 18 strings)

Translation: Tails/wiki/src/sandbox.*.po
Translate-URL: http://translate.tails.boum.org/projects/tails/wikisrcsandboxpo/fr/

In commit 31c44296 this patch was erroneously removed: the restored
patch was *not* upstreamed, so we still need to apply it.

Currently translated at 44.4% (4 of 9 strings)

Currently translated at 44.4% (4 of 9 strings)

I.e. synchronize with the ikiwiki configuration used by our production website.

In the past we recommended forking us on gitlab.com, which was the only mirror
of our main Git repository (aka. tails.git) with a user-friendly "Fork" feature.

Since then, we have another such mirror — Salsa — that we actively use and keep
track of: for example, merge requests can be submitted there and the Foundations
Team will review them. This increases the chances that other teams start to do
the same there as well, until we've decided which GitLab instance will become
the canonical location for our code in the future.

This contrasts with gitlab.com, where we have disabled MRs on purpose.

So, let's point new contributors to a mirror where they can use the common "fork
and send a MR" workflow :)

This number has been decreasing since we wrote the installation
assistant. It went from 39080 in January 2016 down to 8003 in July 2019.