Mark counters as positioners
Some scans like the fscan have positioners which are detected by the writer as normal counters instead of positioners. This is a problem: https://github.com/vasole/pymca/pull/846
Currently the writer makes the distinction between a positioner and a normal counter by looking for triggered_devices
in scan_info["acquisition_chain"]
.
So we need a way to identify or mark a counter as a positioner when not a trigger device.