Predicate needsCtxLocalStep

Holds if there is a local flow step between a ${{ needs.xxx.outputs.yyy }} expression accesing a job output field and the step output itself. But only for those cases where the job (needs) output is defined externally in a MaD Source specification. The reason for this is that we don’t currently have a way to specify that a source starts with a non-empty access path so we cannot write a Source that stores the taint in a Content, we can only do that for steps (storeStep). The easiest thing is to add this local flow step that simulates a read step from the source node for a specific field name.