Merge branch '6.4' into 7.2

* 6.4:
  [Validator] Remove comment to GitHub issue
  [Serializer] Add support for discriminator map in property normalizer
  [DependencyInjection] Fix inlining when public services are involved
  fix contracts directory name
  Fix TraceableSerializer when collected caller from array map
  [HttpClient] Limit curl's connection cache size
  [FrameworkBundle] Fix argument not provided to `add_bus_name_stamp_middleware`

Author: nicolas-grekas

Internal/CurlClientState.php

@@ -50,7 +50,7 @@ public function __construct(int $maxHostConnections, int $maxPendingPushes)
             curl_multi_setopt($this->handle, \CURLMOPT_PIPELINING, \CURLPIPE_MULTIPLEX);
         }
         if (\defined('CURLMOPT_MAX_HOST_CONNECTIONS') && 0 < $maxHostConnections) {
-            $maxHostConnections = curl_multi_setopt($this->handle, \CURLMOPT_MAX_HOST_CONNECTIONS, $maxHostConnections) ? 4294967295 : $maxHostConnections;
+            $maxHostConnections = curl_multi_setopt($this->handle, \CURLMOPT_MAX_HOST_CONNECTIONS, $maxHostConnections) ? min(50 * $maxHostConnections, 4294967295) : $maxHostConnections;
         }
         if (\defined('CURLMOPT_MAXCONNECTS') && 0 < $maxHostConnections) {
             curl_multi_setopt($this->handle, \CURLMOPT_MAXCONNECTS, $maxHostConnections);