Show previous exceptions during bootstrap

[jtattevin]

When an exception is displayed in the console, also output its previous exception when available.
This is especially helpful with PHPStan: if a configuration error occurs, you’ll see the underlying cause instead of only the top‑level failure.

Before :

[ERROR] Rector\NodeTypeResolver\DependencyInjection\PHPStanServicesFactory

or

{"fatal_errors":["Rector\\NodeTypeResolver\\DependencyInjection\\PHPStanServicesFactory"]}

After :

[ERROR] Rector\NodeTypeResolver\DependencyInjection\PHPStanServicesFactory

[ERROR] Unexpected item 'parameters › invalidParameters'.             

or

{"fatal_errors":["Rector\\NodeTypeResolver\\DependencyInjection\\PHPStanServicesFactory","Unexpected item 'parameters › invalidParameters'."]}