[Debug] added the component (closes #6828, closes #6834, closes #7330)

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #6828, #6834, #7330
| License       | MIT
| Doc PR        | symfony/symfony-docs#2479

You can use the individual tools, or register them all:

```php
use Symfony\Component\Debug\Debug;

Debug::enable();
```

Changes in Symfony SE: symfony/symfony-standard#523