fix(esp-tls): make the wolfSSL backend send entire client certificate…

… chains

This change makes the wolfSSL backend sent the complete TLS client certificate
chain. This align the wolfSSL backend with the behavior of the mbedTLS backend.
Some servers need the intermediate certificates to verify a client certificate.
If the provided PEM file contains only a single certificate this change has no effect
and the behavior will be as before.
This impacts higher level APIs to function as someone would expect.
E.g.: esp_websocket_client_config_t.client_cert: when passing here a pem
file containing 2 certificates (the CA's and the client's) it would be
expected that both are transmitted during TLS handshake.

components/esp-tls/esp_tls_wolfssl.c

@@ -97,7 +97,7 @@ static esp_err_t esp_load_wolfssl_verify_buffer(esp_tls_t *tls, const unsigned c
             wolf_fileformat = WOLFSSL_FILETYPE_ASN1;
         }
         if (type == FILE_TYPE_SELF_CERT) {
-            if ((*err_ret = wolfSSL_CTX_use_certificate_buffer( (WOLFSSL_CTX *)tls->priv_ctx, cert_buf, cert_len, wolf_fileformat)) == WOLFSSL_SUCCESS) {
+            if ((*err_ret = wolfSSL_CTX_use_certificate_chain_buffer_format( (WOLFSSL_CTX *)tls->priv_ctx, cert_buf, cert_len, wolf_fileformat)) == WOLFSSL_SUCCESS) {
                 return ESP_OK;
             }
             return ESP_FAIL;