elements: Implement `NotRunnable`.
elements: Implement `NotRunnable`.

Inheritance order of `Tool` and `Workload` had to be changed in order to
inherit `NotRunnable`s `run`.

Signed-off-by: Michael Markert <5eb998b7ac86da375651a4cd767b88c9dad25896@googlemail.com>

fhirschmann/penchy,fhirschmann/penchy