feature #33053 [ErrorHandler] Rework fatal errors (fancyweb)

This PR was merged into the 4.4 branch.

Discussion
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[ErrorHandler] Rework fatal errors

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony/symfony#32605
| License       | MIT
| Doc PR        | -

Built on top of symfony/symfony#33038 so review only the second commit : symfony/symfony@d5c3f7e

The goals of this PR is to replace current "fatal error handlers" with "error enhancers" since all our current fatal error handlers works on \Error since PHP7.

That means we won't use the FatalErrorException anymore, so we will be able to remove it (once we don't need it in the rest of the codebase).

The final goal btw is to handle \Throwable everywhere in the code so we can remove FatalThrowableError & FatalErrorException classes.

Commits
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aaa0cdf523 [ErrorHandler] Rework fatal error handlers

Author: Tobion

Console/Application.php

@@ -20,7 +20,7 @@
 use Symfony\Component\Console\Output\OutputInterface;
 use Symfony\Component\Console\Style\SymfonyStyle;
 use Symfony\Component\DependencyInjection\ContainerAwareInterface;
-use Symfony\Component\ErrorHandler\Exception\FatalThrowableError;
+use Symfony\Component\ErrorHandler\Exception\ErrorException;
 use Symfony\Component\HttpKernel\Bundle\Bundle;
 use Symfony\Component\HttpKernel\Kernel;
 use Symfony\Component\HttpKernel\KernelInterface;
@@ -208,7 +208,7 @@ private function renderRegistrationErrors(InputInterface $input, OutputInterface
 
         foreach ($this->registrationErrors as $error) {
             if (!$error instanceof \Exception) {
-                $error = new FatalThrowableError($error);
+                $error = new ErrorException($error);
             }
 
             $this->doRenderException($error, $output);