Mark shouldStartViewTransition as true when there's an enter animation (#32764)

Typically we mark the name of things that might animate in the snapshot
phase. At the same time we track that should call startViewTransition
too. However, we don't do this for "enter" since they're only marked
later. Leading to having just an "enter" not to animate unless there's
at least another update too.

This tracks if there's a ViewTransitionComponent in the tree that
enters. Luckily we know that from the static flag so we don't have to
traverse it.