Stop running RegTest by default in Trigger ART tests

This MR implements what's been discussed in ATR-20212, namely removes the "RegTest" post-exec step (i.e. log reference comparison) from nearly all Trigger ART tests. Any test where RegTest was added by default with standard settings will no longer have it. Only a handful of tests which relied on reference comparison with specific special settings will still do so. These tests are adapted accordingly.

In the tests where "RegTest" is used to compare trigger counts print-out to a reference, the step is renamed to "CountRefComp" to better reflect its purpose.

This MR has two parts implemented in separate commits. One applies the change to all python-based tests (TrigValSteering framework) and the other applies it to old shell-based tests.