introduce sent/recv extensions field

And remove `extensions_present`

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index a49f774..9947d39 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -8713,8 +8713,14 @@
     *out_len = p - buf;
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3)
-    ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_SIG_ALG;
+    mbedtls_tls13_set_sent_ext_mask( ssl,
+                                     MBEDTLS_TLS_EXT_SIG_ALG );
+    MBEDTLS_SSL_DEBUG_MSG(
+        4, ( "sent %s extension",
+             mbedtls_tls13_get_extension_name(
+                MBEDTLS_TLS_EXT_SIG_ALG ) ) );
 #endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
+
     return( 0 );
 }
 #endif /* MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED */