WIP: Adding onnxruntime example test
This is an attempt to build a test_package in athena/master to test functionality of onnxruntime, available in atlasexternal (https://gitlab.cern.ch/atlas/atlasexternals/tree/master/External/onnxruntime) this WIP is based on !28103 (closed) (closed). I will add more details as my work progresses on this branch. Adding @dguest , @afarbin , @akraszna