GHSA-6j75-5wfj-gh66

### Description

Under some circumstances, the sandbox security checks are not run which allows user-contributed templates to bypass the sandbox restrictions.

The security issue happens when all these conditions are met:

* The sandbox is disabled globally;
* The sandbox is enabled via a sandboxed `include()` function which references a template name (like `included.twig`) and not a `Template` or `TemplateWrapper` instance;
* The included template has been loaded before the `include()` call but in a non-sandbox context (possible as the sandbox has been globally disabled).

### Resolution

The patch ensures that the sandbox security checks are always run at runtime.

### Credits

We would like to thank Fabien Potencier for reporting and fixing the issue.