Add static asserts to container classes.

This will prevent unsupported uses of these classes downstream, which can behave surprisingly and increase the friction of changes to protobuf.  Specifically RepeatedField, RepeatedPtrField, and Map will only be allowed to hold the types listed in https://protobuf.dev/programming-guides/proto.  The old behavior allowed them to hold just about anything, including custom user types.

PiperOrigin-RevId: 502672732