[ticket/16958] Add exception handler for handling uncaught exceptions

[marc1706]

This should improve the user experience a bit when it comes to exceptions being thrown while using phpBB. In addition to certainly having a nicer touch to them visually, they should prevent users of phpBB from ending up at a white page (error 500 style white page).

Checklist:

• Correct branch: master for new features; 3.3.x for fixes
• Tests pass
• Code follows coding guidelines: master and 3.3.x
• Commit follows commit message format

ToDo:

• Check behavior on normal requests
• Check behavior on AJAX requests
• Check potential use in installer

Screenshots:

• Debug disabled:
• Debug enabled:
• Debug enabled and display of arguments enabled in php.ini:
  

Tracker ticket (set the ticket ID to your ticket ID):

https://tracker.phpbb.com/browse/PHPBB3-16958

[marc1706]

I've marked this as WIP for now as I still want to test the behavior on other pages.

[marc1706]

Working on proper errors during ajax requests as well:

[3D-I]

Working on proper errors during ajax requests as well

Also with debug enabled?

[marc1706]

Working on proper errors during ajax requests as well

Also with debug enabled?

In ajax requests I have opted to not add a backtrace.

[Derky]

It's looking good, but I've some testing results:

1. SQL errors are HTML escaped twice in the gray box:

2. When using an incorrect database password I get a white page instead of an error message in this styling.

3. If a PHP error occurs during an AJAX request (for example a variable doesn't exist on an object) the error is hidden with a "something went wrong" in the AJAX pop-up. But you can no longer see the actual error message if you open up the network tab to see the AJAX response. The original error should also be returned from this endpoint and ideally be shown in the pop-up as well.
   Original behaviour: (able to find the actual error message)

Current (this PR) behaviour: (impossible to find the actual error message)

[rubencm]

The exceptions that are thrown from phpbb (runtime_exception for example), are multilanguage, since the message is a language variable and they have an additional constructor parameter for the language parameters. Maybe you could try translating them if the exception is an instance of runtime_exception or implements exception_interface.

One more thing, as I report here https://tracker.phpbb.com/browse/PHPBB3-16198 the component we are using to handle errors is discontinued, I don't know if it is worth developing on top of it, or better update it first

[rubencm]

Then you can remove symfony/debug in composer.json

You should replace symfony/debug by symfony/error-component in composer.json

[rubencm]

Update symfony/error-component to ^6.3 (#6528)