Use zoom steps lower than 1. This allows to zoom out a high-res
image. For example, before it was not possible to maker 4K image
to fit on FullHD monitor.
Also, don't force zoom to be above 1. Not sure why that was done,
but this disallows zooming out.
It is still not possible to zoom in higher than the window size
allows. In order to support this the player needs to be refactored
in a way that allows to decouple zoom from window size.
Fixes T59177: Animplayer extreme zooms in when playing rendered animation
9eee2aa20c