This also changes MessageView and MessageMut to be subtraits of the ViewProxy and MutProxy (which also requires them to have lifetimes now, and a weird extra bounds on ViewProxy)
PiperOrigin-RevId: 654788207
This doesn't _actually_ make the C++ Kernel path ever fail yet, but now that the API is a Result<SerializedData, SerializeError> it can be fixed as an implementation detail.
PiperOrigin-RevId: 638329136
For now, these are limited to tests of text-form for delimited fields that locks down our problematic behavior in editions. Follow up changes will adjust the behavior to behave better under editions.
PiperOrigin-RevId: 622211473