[FrameworkBundle] enable ErrorHandler in prod

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11053, #8281
| License       | MIT
| Doc PR        | -

-  a new debug.error_handler service is the registered PHP error handler, with ErrorHandler::register() as factory
- ErrorHandler::register() is patched so that it checks if the currently registered error handler is an instance of ErrorHandler - in which case it returns this instance and don't create a new one.
- DebugHandlersListener now listen to ConsoleEvents and re-injects fatal errors within the $app->renderException code path
- DebugHandlersListener also has a new $scream parameter to control is silenced errors are logged or not
Now that it is private I can drop you're right.
I may reintroduce it later to bind it to new configuration option for controlling scope_at and trace_at,
that's why I added it in the first place.
Removing for now.