Rework run_cmd in test_util.py to simplify API

Currently test_util.py can only test 'ade sysroot'. Additionnaly
it uses about 3 different python syntaxes for parameters. *args
is used for the majority of parameters, path and config are passed as
**kwargs. Finally command, is a positionnal argument.

In order for ade functions other than sysroot can thus be tested,
simplify run_cmd api so that in only take (*args) wth direct arguments.
This means changing all the should_succeed and should_fail calls so
that they no longer assume 'sysroot' is the command to be tested.

Apertis: https://phabricator.apertis.org/T3777



Signed-off-by: Frédéric Dalleau <frederic.dalleau@collabora.com>
Reviewed-by: Emanuele Aina <emanuele.aina@collabora.com>
Differential Revision: https://phabricator.apertis.org/D6410