Revert "[TASK] Configure frontend caches with NullBackend (#321)"

This reverts commit c32fe20.

Setting some cache configurations to NullBackend needs adoption
in core tests. Therefore, the backport to set the new caches to
NulLBackend is reverted.

The removed non-existing `extbase_object` NullBackend configuration
stays removed.

Classes/Core/Functional/FunctionalTestCase.php

@@ -24,6 +24,7 @@
 use Psr\Container\ContainerInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use TYPO3\CMS\Core\Authentication\BackendUserAuthentication;
+use TYPO3\CMS\Core\Cache\Backend\NullBackend;
 use TYPO3\CMS\Core\Context\Context;
 use TYPO3\CMS\Core\Context\UserAspect;
 use TYPO3\CMS\Core\Core\Bootstrap;
@@ -373,14 +374,6 @@ protected function setUp(): void
             $localConfiguration['SYS']['trustedHostsPattern'] = '.*';
             $localConfiguration['SYS']['encryptionKey'] = 'i-am-not-a-secure-encryption-key';
             $localConfiguration['GFX']['processor'] = 'GraphicsMagick';
-            // Set cache backends to null backend instead of database backend let us save time for creating
-            // database schema for it and reduces selects/inserts to the database for cache operations, which
-            // are generally not really needed for functional tests. Specific tests may restore this in if needed.
-            $localConfiguration['SYS']['caching']['cacheConfigurations']['hash']['backend'] = 'TYPO3\\CMS\\Core\\Cache\\Backend\\NullBackend';
-            $localConfiguration['SYS']['caching']['cacheConfigurations']['imagesizes']['backend'] = 'TYPO3\\CMS\\Core\\Cache\\Backend\\NullBackend';
-            $localConfiguration['SYS']['caching']['cacheConfigurations']['pages']['backend'] = 'TYPO3\\CMS\\Core\\Cache\\Backend\\NullBackend';
-            $localConfiguration['SYS']['caching']['cacheConfigurations']['pagesection']['backend'] = 'TYPO3\\CMS\\Core\\Cache\\Backend\\NullBackend';
-            $localConfiguration['SYS']['caching']['cacheConfigurations']['rootline']['backend'] = 'TYPO3\\CMS\\Core\\Cache\\Backend\\NullBackend';
             $testbase->setUpLocalConfiguration($this->instancePath, $localConfiguration, $this->configurationToUseInTestInstance);
             $defaultCoreExtensionsToLoad = [
                 'core',