ART test to generate HLT json diff between CA and legacy config

This reproduces the legacy v1PhysP1 dumpConfig test, then runs a CA version of this, each in their own clean directory. The HLT JO json is then compared with confTool.py, then run through a python script that eliminates selected irrelevant lines -- both the full output and the sanitised version will be kept. Useful for comparing properties of components. N.B. some restructuring of the sequences in the CA menu construction may result in spurious cases of hypo algs seemingly missing from some step sequences.

To make this work it was necessary to add a workdir property to TrigValSteering.Step. If defined, we create and cd to the specified workdir and then return to the previous dir on completion. I put some protections against defining paths that obviously could lead outside the CWD.

Example output in attachment on ATR-28500.