Add Laravel testing doc and reorganize old testing docs

[vinceAmstoutz]

As discussed in our messages with @dunglas, I will take the following steps:

• Create a Documentation File for Laravel: I will create a new document titled laravel/testing.md that describes how to write tests using Pest and PHPUnit in Laravel.
• Reorganize Symfony Documentation: To improve separation of concerns, I will move the Symfony-related content from core/testing.md into symfony/testing.md.
• Maintain Core Documentation: The core/testing.md file will remain the central resource for testing documentation encompassing both Symfony and Laravel.

[dunglas]

Maybe can you keep the root core/testing.md file, move most of its content in symfony/testing.md directly (no need for two files IMHO), add a new laravel/testing.md file, and reference the Laravel and Symfony testing docs in docs/testing.md.

This will prevent setting redirections.

[vinceAmstoutz]

Maybe can you keep the root core/testing.md file, move most of its content in symfony/testing.md directly (no need for two files IMHO), add a new laravel/testing.md file, and reference the Laravel and Symfony testing docs in docs/testing.md.

This will prevent setting redirections.

Indeed, that's better, I'll do that!