…ig-builders from config files (nicolas-grekas)

This PR was merged into the 7.4 branch.

Discussion
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[DependencyInjection] Handle returning arrays and config-builders from config files

| Q             | A
| ------------- | ---
| Branch?       | 7.4
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Issues        | -
| License       | MIT

Another step on the path explored in #58771

This allows returning PHP arrays or config-builders from config files.

Several styles are supported, some examples below.

What this does *not* support is config trees under the `import`, `parameters` or `services` namespaces (that's for another PR).

Arrays:
```php
return [
    'framework' => [...],
];
```

```php
return static function () {
    yield 'framework' => [...];
];
```

Config builders (best DX together with #61879):

```php
return new FrameworkConfig([...]);
```

```php
return static function () {
    return new FrameworkConfig([...]);
];
```

```php
// $env is always available in config files
if ('dev' === $env) {
    return new FrameworkConfig([...]);
}
```

```php
return static function (string $env) {
    if ('dev' === $env) {
        yield new FrameworkConfig([...]);
    }
};
```

Commits
-------

ff3fbd7 [DependencyInjection] Handle returning arrays and config-builders from config files