…to show `HttpKernel::handle()` will catch throwables (Nyholm)

This PR was merged into the 6.2 branch.

Discussion
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[FrameworkBundle][HttpKernel] Add deprecation warning to show `HttpKernel::handle()` will catch throwables

| Q             | A
| ------------- | ---
| Branch?       | 6.2
| Bug fix?      | no
| New feature?  | no
| Deprecations? | yes
| Tickets       | Fix #16205
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!-- required for new features -->

I suggest that starting from Symfony 7.0 the `HttpKernel` will start to catch `\Throwable` and convert them to a `Response`.

This was first asked in #16205, I face a similar issue with Runtime component and Bref..

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The reason I push for this change is to embrace the request/response workflow of the Kernel without trusting the custom error handler. In an environment where you serve multiple requests with the same PHP process (read: RoadRunner, Swoole, Bref) you would write something like:

```php
$kernel = new Kernel('prod', false);
while (true) {
  $request = /* create sf request from custom environment */
  try {
    $response = $kernel->handle(request);
    return ResponseConverter::convert($response);
  } catch (\Throwable $e) {
    exit(1);
  }
}
```
(pseudo code of course. Here is a [real example](https://github.com/php-runtime/bref/blob/0.3.1/src/BrefRunner.php#L30-L43))

The `exit(1)` means a hard crash. For Bref Runtime it would result in a 500 error from API-gateway. Since the `\Throwable` is caught, the Symfony error handler is not used. If we would not to catch the `\Throwable`, then the Symfony error handler would be used, but it would print a Response instead of returning it. (Printing a response will just add HTML on the CLI...)

-----------

Other PRs and issues related to this:

- #45301
- #26514
- #22128
- #36885
- #25467

I'm happy to let the `HttpKernel` to catch the `\Throwable` exception right now, but I thought this very conservative PR would have a higher change to get merged.

Also note that we do not specify any behaviour on our [HttpKernelInterface](https://github.com/symfony/symfony/blob/v6.0.7/src/Symfony/Component/HttpKernel/HttpKernelInterface.php#L43)

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To remove the deprecation message you need to add this to your config:

```yaml
framework:
    catch_all_throwables: true
```

Commits
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7977a15 Add deprecation warning to show HttpKernel::handle() will catch throwables