Conflicts with #5547 (Animated Zoom) resolved in wheel_nav.rs, canvas.rs and
panels.rs: the Navigator and canvas pass both Animated Zoom and
!animations_off; with Animation Effects off, the sideways part of an
animated wheel zoom pans by the frame's own events folded by their
modifiers (#4573's unsmoothed scroll) instead of the plain-event raw.x,
so Ctrl + wheel still pans sideways there. #4573's modifier test runs
with Animated Zoom off and on.