Merge branch '5.1' into 5.x

* 5.1:
  [Contracts] add branch-aliases for dev-main
  [Cache] Make Redis initializers static
  [Messenger] Fixed typos in Connection
  [CI] Fixed build on AppVeyor
  Fix tests typo
  [Lock] Reset Key lifetime time before we acquire it
  [CI] Silence errors when remove file/dir on test tearDown()
  Fix tests
  Remove content-type check on toArray methods

Author: nicolas-grekas

composer.json

@@ -26,5 +26,8 @@
             "/Tests/"
         ]
     },
-    "minimum-stability": "dev"
+    "minimum-stability": "dev",
+    "extra": {
+        "branch-version": "5.2"
+    }
 }