Merge branch '6.4' into 7.0

* 6.4:
  skip tests that do not work with ICU 71.1
  [DependencyInjection] Fix dumping containers with null-referenced services
  [Routing] Fix removing aliases pointing to removed route in RouteCollection::remove()
  [VarExporter] Fix lazy ghost trait when using nullsafe operator
  [Routing] Fix conflicting FQCN aliases with route name
  Fix legacy class palceholder definitions for static analysis

Tests/Extension/Core/Type/DateTypeTest.php

@@ -15,6 +15,7 @@
 use Symfony\Component\Form\Exception\LogicException;
 use Symfony\Component\Form\FormError;
 use Symfony\Component\Form\FormInterface;
+use Symfony\Component\Intl\Intl;
 use Symfony\Component\Intl\Util\IntlTestHelper;
 use Symfony\Component\OptionsResolver\Exception\InvalidOptionsException;
 
@@ -92,6 +93,10 @@ public function testSubmitFromSingleTextDateTime()
         // we test against "de_DE", so we need the full implementation
         IntlTestHelper::requireFullIntl($this, false);
 
+        if ('71.1' === Intl::getIcuVersion()) {
+            $this->markTestSkipped('Skipping test due to a bug in ICU 71.1.');
+        }
+
         \Locale::setDefault('de_DE');
 
         $form = $this->factory->create(static::TESTED_TYPE, null, [
@@ -114,6 +119,10 @@ public function testSubmitFromSingleTextDateTimeImmutable()
         // we test against "de_DE", so we need the full implementation
         IntlTestHelper::requireFullIntl($this, false);
 
+        if ('71.1' === Intl::getIcuVersion()) {
+            $this->markTestSkipped('Skipping test due to a bug in ICU 71.1.');
+        }
+
         \Locale::setDefault('de_DE');
 
         $form = $this->factory->create(static::TESTED_TYPE, null, [
@@ -137,6 +146,10 @@ public function testSubmitFromSingleTextString()
         // we test against "de_DE", so we need the full implementation
         IntlTestHelper::requireFullIntl($this, false);
 
+        if ('71.1' === Intl::getIcuVersion()) {
+            $this->markTestSkipped('Skipping test due to a bug in ICU 71.1.');
+        }
+
         \Locale::setDefault('de_DE');
 
         $form = $this->factory->create(static::TESTED_TYPE, null, [
@@ -159,6 +172,10 @@ public function testSubmitFromSingleTextTimestamp()
         // we test against "de_DE", so we need the full implementation
         IntlTestHelper::requireFullIntl($this, false);
 
+        if ('71.1' === Intl::getIcuVersion()) {
+            $this->markTestSkipped('Skipping test due to a bug in ICU 71.1.');
+        }
+
         \Locale::setDefault('de_DE');
 
         $form = $this->factory->create(static::TESTED_TYPE, null, [
@@ -183,6 +200,10 @@ public function testSubmitFromSingleTextRaw()
         // we test against "de_DE", so we need the full implementation
         IntlTestHelper::requireFullIntl($this, false);
 
+        if ('71.1' === Intl::getIcuVersion()) {
+            $this->markTestSkipped('Skipping test due to a bug in ICU 71.1.');
+        }
+
         \Locale::setDefault('de_DE');
 
         $form = $this->factory->create(static::TESTED_TYPE, null, [