Add support for TLS 1.3 cookie extension
That is, the cookie extension from: https://tools.ietf.org/html/draft-ietf-tls-tls13-20
We should make sure that it aligns, if possible, with the current cookie handling for DTLS 1.2.
That is, the cookie extension from: https://tools.ietf.org/html/draft-ietf-tls-tls13-20
We should make sure that it aligns, if possible, with the current cookie handling for DTLS 1.2.