Cleanup legacy overlay transforms and update ART tests
This MR removes the old OverlayPool_tf.py
and OverlayBS_tf.py
skeletons (ATLASSIM-5649) and removes/updates the relevant ART tests (ATLASSIM-5504, ATLASSIM-5587).
Also fixes conditions that are not in the used global tag (ATLASSIM-5504).
Finally MT tests are updated to MC20e, again to fix conditions access (ATLASSIM-5644).
Note that this will change the output also of some of the existing Overlay MT tests.
Please do not squash as commits are nicely separated.
/cc @jchapman