ExpandableListitem: fall back to animation speed under our control
requested to merge ngraham/plasma-framework:fall-back-to-animation-speed-under-our-control into master
The current code respects the value of highlightResizeDuration, if the parent ListView set a value for it. If not, it falls back to -1, which resets the value to the upstream Qt default value of 400ms. This value is itself hardcoded and does not respect the systemwide animation duration speed in Plasma.
To correct this, instead fall back to Kirigami.Units.longDuration, which is under our control, does respect the animation speed setting, and it's a bit faster too, which feels nicer.