Merge branch '7.4' into 8.0

* 7.4:
  [Validator][Serializer] Make internal properties private
  [VarExporter] Fix serializing classes with __serialize() returning unprefixed private properties
  Remove direct access to internal properties cross-components
  remove deprecated nullable option from primary key columns
  [Validator] Optimize serialized metadata and cleanup tests
  specific fix to avoid 'outag' when inflecting 'outages'
  Use <info> for options in command description
  [ObjectMapper] Remove obsolete TODO
  [HttpFoundation][HttpKernel][WebProfilerBundle] Add support for the `QUERY` HTTP method
  [DependencyInjection] Don’t autowire excluded services
  Add bool return type to CustomCredentials callable parameter
  [Process] Enhance hasSystemCallBeenInterrupted function for non-english locale
  [FrameworkBundle] Make `cache:warmup` warm up read-only caches

Author: nicolas-grekas

Tests/Extension/Validator/ValidatorExtensionTest.php

@@ -42,8 +42,8 @@ public function test2Dot5ValidationApi()
         $this->assertCount(1, $metadata->getConstraints());
         $this->assertInstanceOf(FormConstraint::class, $metadata->getConstraints()[0]);
 
-        $this->assertSame(CascadingStrategy::NONE, $metadata->cascadingStrategy);
-        $this->assertSame(TraversalStrategy::NONE, $metadata->traversalStrategy);
+        $this->assertSame(CascadingStrategy::NONE, $metadata->getCascadingStrategy());
+        $this->assertSame(TraversalStrategy::NONE, $metadata->getTraversalStrategy());
         $this->assertCount(0, $metadata->getPropertyMetadata('children'));
     }
 }