Implement proposal 332 (ntor v3, with extra data)
We should implement
332-ntor-v3-with-extra-data, a new ntor variant that allows the client to send authenticated encrypted data with their handshake, and get an authenticated encrypted response with the server's handshake.
We will need this for proposal 324, in order to implement negotiation for the SENDME window size.
See #40377 (closed) for discussion of the proposal.