Merge branch '5.0' into 5.1

* 5.0: (28 commits)
  [Cache] $lifetime cannot be null
  [Serializer] minor cleanup
  fix merge
  Run PHP 8 as 7.4.99
  Remove calls to deprecated ReflectionParameter::getClass().
  [VarDumper] fix PHP 8 support
  Add php 8 to travis.
  [Cache] Accessing undefined constants raises an Error in php8
  [Cache] allow DBAL v3
  Skip Doctrine DBAL on php 8 until we have a compatible version.
  [DomCrawler] Catch expected ValueError.
  Made method signatures compatible with their corresponding traits.
  [ErrorHandler] Apply php8 fixes from Debug component.
  [DomCrawler] Catch expected ValueError.
  [Validator] Catch expected ValueError.
  [VarDumper] ReflectionFunction::isDisabled() is deprecated.
  [BrowserKit] Raw body with custom Content-Type header
  [PropertyAccess] Parse php 8 TypeErrors correctly.
  [Intl] Fix call to ReflectionProperty::getValue() for static properties.
  [HttpKernel] Prevent calling method_exists() with non-string values.
  ...

Tests/NumberFormatter/AbstractNumberFormatterTest.php

@@ -600,7 +600,7 @@ public function testGetSymbol()
 
         $r = new \ReflectionProperty('Symfony\Component\Intl\NumberFormatter\NumberFormatter', 'enSymbols');
         $r->setAccessible(true);
-        $expected = $r->getValue('Symfony\Component\Intl\NumberFormatter\NumberFormatter');
+        $expected = $r->getValue();
 
         for ($i = 0; $i <= 17; ++$i) {
             $this->assertSame($expected[1][$i], $decimalFormatter->getSymbol($i));
@@ -617,7 +617,7 @@ public function testGetTextAttribute()
 
         $r = new \ReflectionProperty('Symfony\Component\Intl\NumberFormatter\NumberFormatter', 'enTextAttributes');
         $r->setAccessible(true);
-        $expected = $r->getValue('Symfony\Component\Intl\NumberFormatter\NumberFormatter');
+        $expected = $r->getValue();
 
         for ($i = 0; $i <= 5; ++$i) {
             $this->assertSame($expected[1][$i], $decimalFormatter->getTextAttribute($i));