Fix use of TrigDecisionTool in simple macro, and add example as a unittest - Restore capability for EventLoopMgr to fire incidents

This MR will hopefully help preserve the knowledge of how to do simple tests with tools outside of a package-based environment.

The MR restores the capability for the AthenaEventLoopMgr to fire incidents that are needed by various tools. This is essential in the case of a simple eventloop job, which would otherwise require the scheduling of the AthIncFirerAlg in such loops.