BUG/MEDIUM: ssl: AWS-LC + TLSv1.3 won't do ECDSA in RSA+ECDSA configuration

BUG/MEDIUM: ssl: AWS-LC + TLSv1.3 won't do ECDSA in RSA+ECDSA configuration

SSL_get_ciphers() in AWS-LC seems to lack the TLSv1.3 ciphersuites,
which break the ECDSA key selection when doing TLSv1.3.

An issue was opened https://github.com/aws/aws-lc/issues/1638

Indeed, in ssl_sock_switchctx_cbk(), the sigalgs is used to determine if
ECDSA is doable or not, then the function compares the list of ciphers in
the clienthello with the list of configured ciphers.

The fix solves the issue by never skipping the TLSv1.3 ciphersuites,
even if they are not in SSL_get_ciphers().