[Fiber] Wait for suspensey image in the viewport before starting an animation (#34500)

Stacked on #34486.

If we gave up on loading suspensey images for blocking the commit (e.g.
due to #34481), we can still block the view transition from committing
to allow an animation to include the image from the start.

At this point we have more information about the layout so we can
include only the images that are within viewport in the calculation
which may end up with a different answer.

This only applies when we attempt to run an animation (e.g. something
mutated inside a `<ViewTransition>` in a Transition). We could attempt a
`startViewTransition` if we gave up on the suspensey images just so that
we could block it even if no animation would be running.

However, this point the screen is frozen and you can no longer have sync
updates interrupt so ideally we would have already blocked the commit
from happening in the first place.

The reason to have two points where we block is that ideally we leave
the UI responsive while blocking, which blocking the commit does. In the
simple case of all images or a single image being within the viewport,
that's favorable. By combining the techniques we only end up freezing
the screen in the special case that we had a lot of images added outside
the viewport and started an animation with some image inside the
viewport (which presumably is about to finish anyway).