GHSA-hppc-g8h3-xhp3: rust-openssl: Unchecked callback length in PSK/cookie trampolines leaks adjacent memory to peer

The FFI trampolines behind SslContextBuilder::set_psk_client_callback, set_psk_server_callback, set_cookie_generate_cb, and set_stateless_cookie_generate_cb forwarded the user closure’s returned usize directly to OpenSSL without checking it against the &mut [u8] that was handed to the closure. This can lead to buffer overflows and other unintended consequences.