Migrate jenkins nodes to bullseye

This means following the plan [3] for:

• jenkins-debian1: the debian package build node [1]
• thyssen: jenkins server node [2]

It should be fine to just upgrade the nodes as their respective major tooling are part of debian packages.

• [1] The main tools here are sbuild and chroot.

• [2] The main tooling are within docker constraint (so it's "pinned")

• [3]

task=#3770
puppet agent --disable "$task: dist-upgrade to bullseye"
cd /etc
sed -i -e 's/buster/bullseye/' /etc/apt/sources.list.d/*
sed -i -e 's,bullseye/updates,bullseye-security,' /etc/apt/sources.list.d/debian-security.list
git status
grep bullseye-security /etc/apt/sources.list.d/debian-security.list
git add .
git commit -m "$task: Migrate sources.list to bullseye"
apt update
apt upgrade -y
apt dist-upgrade -y
reboot
puppet agent --enable && puppet agent --test

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Migrated from T3770 (view on Phabricator)