HTTP/3: fixed server_name regex captures (ticket #2407).

Previously, HTTP/3 stream connection didn't inherit the servername regex
from the main QUIC connection saved when processing SNI and using regular
expressions in server names.  As a result, it didn't execute to set regex
captures when choosing the virtual server while parsing HTTP/3 headers.

src/http/v3/ngx_http_v3_request.c

@@ -81,6 +81,7 @@ ngx_http_v3_init(ngx_connection_t *c)
 
     if (phc->ssl_servername) {
         hc->ssl_servername = phc->ssl_servername;
+        hc->ssl_servername_regex = phc->ssl_servername_regex;
         hc->conf_ctx = phc->conf_ctx;
 
         ngx_set_connection_log(c, clcf->error_log);