Actually, docker is used to test Linux packages once they are built.
The packaging process is done on the host system where package.py is
run.

Consequences:
    * difficult to reproduce an exact same build on another host
    * changing a Debian/Ubuntu target version means some upgrade steps
      on the build host (mix that with the fact that the host also
      could build old Odoo versions)
    * Fedora rpm package is built on an Ubuntu system (which is not a
      real problem but it could be)

With this commit, the package.py utility is refactored to use Docker
containers to build the Gnu/Linux packages.

closes odoo/odoo#39091

Signed-off-by: Christophe Monniez (moc) <moc@odoo.com>