Allow triggering WA workloads from inside LISA

Created by: bjackman

We currently use the wltests system to run WA agendas via the shell, then use LISA to analyse the results. Perhaps it could be useful instead to have LISA directly run WA workloads. This was implemented by https://github.com/ARM-software/lisa/pull/120 but that is now outdated, it would need to be replaced with WA3-compatble version.