John Swinbank, smallish review for you that should hopefully be somewhat familiar: this fixes the recursive aliases you saw on
DM-1674, where were due to the plugin algorithms being initialized before the slots; that ordering subverted code that was supposed to resolve some aliases immediately. I've also added code to check for that condition and throw, and that in turn required changes to a bunch of test code that was also initializing them out of order.
All changes are on meas_base tickets/
DM-3400; I'll kick off a CI run now, and there's a chance that will inspire some changes to other packages, but they should be trivial.