The piuparts job should mimic piuparts.debian.org as much as possible

Discussing with @olasd during DebConf24, it seems there would be a good idea to reduced the differences about how piuparts is run in Salsa CI and in piuparts.d.o. For example, piuparts.d.o relies on debootstrap and chroots to carry out the test, while Salsa CI is using docker-in-docker. Contrary to piuparts.d.o, the Salsa CI chroot also includes deb822 source files, and this mismatch causes packages not being installable because piuparts overwrites the sources.list. See: #227, #292 (closed).

The piuparts.d.o instances configuration can be found at https://salsa.debian.org/debian/piuparts/tree/develop/instances.

Also piuparts.d.o runs the piuparts from the development git branch. Running sid is not so bad though.