feature symfony#54657 [TwigBundle] Deprecate base_template_class option (Steveb-p)

This PR was merged into the 7.1 branch.

Discussion
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[TwigBundle] Deprecate `base_template_class` option

| Q             | A
| ------------- | ---
| Branch?       | 7.1
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | yes <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Issues        | <!-- prefix each issue number with "Fix #", no need to create an issue if none exists, explain below instead -->
| License       | MIT

According to https://github.com/twigphp/Twig/blob/3.x/CHANGELOG#L222, `base_template_class` option has been removed from Twig 3.0.

Symfony still allows to pass this configuration option via https://github.com/symfony/symfony/blob/7.1/src/Symfony/Bundle/TwigBundle/DependencyInjection/Configuration.php#L132, but there is of course no effect.

I think it would be good to deprecate it and prepare it's removal in 8.x? Since Symfony 7.x requires Twig 3.x.

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Commits
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c30d14f Deprecate Twig Bundle `base_template_class` option

Author: fabpot

src/Symfony/Bundle/TwigBundle/DependencyInjection/Configuration.php

@@ -129,7 +129,11 @@ private function addTwigOptions(ArrayNodeDefinition $rootNode): void
             ->children()
                 ->scalarNode('autoescape_service')->defaultNull()->end()
                 ->scalarNode('autoescape_service_method')->defaultNull()->end()
-                ->scalarNode('base_template_class')->example('Twig\Template')->cannotBeEmpty()->end()
+                ->scalarNode('base_template_class')
+                    ->setDeprecated('symfony/twig-bundle', '7.1')
+                    ->example('Twig\Template')
+                    ->cannotBeEmpty()
+                ->end()
                 ->scalarNode('cache')->defaultValue('%kernel.cache_dir%/twig')->end()
                 ->scalarNode('charset')->defaultValue('%kernel.charset%')->end()
                 ->booleanNode('debug')->defaultValue('%kernel.debug%')->end()