Merge branch '5.1'

* 5.1:
  [Notifier] Notifier 5.2 is incompatible with 5.1 bridges.
  [DI] fix minor perf regression when creating non-shared services

Author: nicolas-grekas

composer.json

@@ -20,7 +20,17 @@
         "symfony/polyfill-php80": "^1.15"
     },
     "conflict": {
-        "symfony/http-kernel": "<4.4"
+        "symfony/http-kernel": "<4.4",
+        "symfony/firebase-notifier": "<5.2",
+        "symfony/free-mobile-notifier": "<5.2",
+        "symfony/mattermost-notifier": "<5.2",
+        "symfony/nexmo-notifier": "<5.2",
+        "symfony/ovh-cloud-notifier": "<5.2",
+        "symfony/rocket-chat-notifier": "<5.2",
+        "symfony/sinch-notifier": "<5.2",
+        "symfony/slack-notifier": "<5.2",
+        "symfony/telegram-notifier": "<5.2",
+        "symfony/twilio-notifier": "<5.2"
     },
     "autoload": {
         "psr-4": { "Symfony\\Component\\Notifier\\": "" },