Add unit tests for sysroot management tool

 * There is one test file for each individual sysroot subcommands.
 * The /tmp directory is used when an installation directory is needed.
 * Tests are not installed for now and need the 'ade' executable to be
   in the 'tools' directory.

Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Reviewed-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D4815