CVE-2026-1677 net: TLS 1.2 connections allowed on TLS 1.3 sockets

Zephyr sockets created with IPPROTOTLS13 can still negotiate a TLS 1.2 connection when both TLS versions are enabled in Kconfig, because the socket-level protocol selection is not propagated to mbedTLS e.g. via mbedtlssslconfmintlsversion. The ClientHello advertises both versions and the peer can...