bug: doesn't yet work with pyside6

[tlambert03]

known issue, sliders don't work, and there are segfaults... not sure whether this is an ndv issue or a superqt issue (pyside6 has been problematic recently, but even going back to 6.5 it doesn't work)

[tlambert03]

turns out the issue is ensure_main_thread from superqt. i don't think it's working as expected for pyside6

[tlambert03]

note also that DimsSliders.valueChanged needs to be changed from Signal(dict) to Signal(object) in order to work for PySide (even though it is actually a dict). Otherwise, pyside just eats it and returns an empty dict??

[tlambert03]

this is enough of a pain that I'm going to put this on the backburner until someone comes along needing this in pyside instead of pyqt. Most of this isn't related to ndv, but rather to multi-threading concurrency that ndv is doing, and some of superqt utils not working well with recent pyside