…entations for `MicroKernelTrait::registerBundles()` and `getProjectDir()` (nicolas-grekas)

This PR was merged into the 5.1-dev branch.

Discussion
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[FrameworkBundle] Added flex-compatible default implementations for `MicroKernelTrait::registerBundles()` and `getProjectDir()`

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

I think it's safe now to migrate some flex-based defaults from the recipe to the bundle.
No BC break here as all existing kernels already redefine this method.

Commits
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a689807 [FrameworkBundle] Added flex-compatible default implementations for `MicroKernelTrait::registerBundles()` and `getProjectDir()`

…in MicroKernelTrait::configureContainer() (nicolas-grekas)

This PR was merged into the 5.1-dev branch.

Discussion
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[FrameworkBundle] Allow using a ContainerConfigurator in MicroKernelTrait::configureContainer()

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

This PR is a continuation of #32937 (it reverts some parts of it that are not needed anymore). It builds on #34872 for now.

This PR allows using the PHP-DSL natively in our `Kernel::configureContainer()` methods.
It allows the same in our `Kernel::configureRoutes()` methods.

Both signatures are handled gracefully with no deprecations to let existing code in peace:
- `protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader);`
- `protected function configureContainer(ContainerConfigurator $c);` (a loader is always passed as 2nd arg to ease FC)

Same for routes:
- `protected function configureRoutes(RoutingConfigurator $routes);`
- `protected function configureRoutes(RouteCollectionBuilder $routes);` (this one is deprecated because `RouteCollectionBuilder` is deprecated)

Here is my working `src/Kernel.php` after this change:

```php
class Kernel extends BaseKernel
{
    use MicroKernelTrait;

    protected function configureContainer(ContainerConfigurator $container): void
    {
        $container->import('../config/{packages}/*.yaml');
        $container->import('../config/{packages}/'.$this->environment.'/*.yaml');
        $container->import('../config/services.yaml');
        $container->import('../config/{services}_'.$this->environment.'.yaml');
    }

    protected function configureRoutes(RoutingConfigurator $routes): void
    {
        $routes->import('../config/{routes}/'.$this->environment.'/*.yaml');
        $routes->import('../config/{routes}/*.yaml');
        $routes->import('../config/routes.yaml');
    }
}
```

Commits
-------

cf45eec [FrameworkBundle] Allow using a ContainerConfigurator in MicroKernelTrait::configureContainer()

… of controllers and service factories (nicolas-grekas)

This PR was merged into the 5.1-dev branch.

Discussion
----------

[FrameworkBundle] Allow using the kernel as a registry of controllers and service factories

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | Fix #28992, fix #29997
| License       | MIT
| Doc PR        | -

This PR builds on #34873 and #34872 and allows using the `Kernel` as a registry of autowired controllers and service factories. The `ContainerConfigurator` passed to `configureContainer()` defaults to declaring autowired and autoconfigured services.

TL;DR: Silex is back but in a much more powerful way \o/

Here is a Kernel that just works and displays `Hello App\Foo` on the `/` route:
```php
class Kernel extends BaseKernel
{
    use MicroKernelTrait;

    protected function configureContainer(ContainerConfigurator $container): void
    {
        $container->services()
            ->load('App\\', '../src')
            ->set(Foo::class)
                ->factory([$this, 'createFoo']);
    }

    public function createFoo(Bar $bar)
    {
        return new Foo($bar);
    }

    protected function configureRoutes(RoutingConfigurator $routes): void
    {
        $routes->add('home', '/')->controller([$this, 'helloAction']);
    }

    public function helloAction(Foo $foo)
    {
        return new Response('Hello '.get_class($foo));
    }
}
```

Commits
-------

9c9b99c [FrameworkBundle] Allow using the kernel as a registry of controllers and service factories