Add a test for CVE-2021-3449
Add a test for CVE-2021-3449

We perform a reneg handshake, where the second ClientHello drops the
sig_algs extension. It must also contain cert_sig_algs for the test to
work.

Reviewed-by: Tomas Mraz <2bc6038c3dfca09b2da23c8b6da8ba884dc2dcc2@openssl.org>
Reviewed-by: Paul Dale <ddec78389666b4f7c9b4d110380c848489a3e4aa@openssl.org>

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl