dillon1000/react

Merge ViewTransition layout/onLayout props into update/onUpdate (#32723)

We currently have the ability to have a separate animation for a
ViewTransition that relayouts but doesn't actually have any internal
mutations. This can be useful if you want to separate just a move from
for example flashing an update.

However, we're concerned that this might be more confusion than its
worth because subtle differences in mutations can cause it to trigger
the other case. The existence of the property name might also make you
start looking for it to solve something that it's not meant for.

We already fallback to using the "update" property if it exists but
layout doesn't. So if we ever decide to add this back it would backwards
compatible. We've also shown in implementation that it can work.