feature #45512 [DependencyInjection] Allow using expressions as service factories (nicolas-grekas, jvasseur)

This PR was squashed before being merged into the 6.1 branch.

Discussion
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[DependencyInjection] Allow using expressions as service factories

| Q             | A
| ------------- | ---
| Branch?       | 6.1
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | yes
| Tickets       | -
| License       | MIT
| Doc PR        | -

Replaces #45447

This PR allows using expressions as service factories:
- in YAML: `factory: '@=service("foo").bar()'`
- in PHP:  `->factory(expr('service("foo").bar()'))`
- in XML: `<factory expression="service('foo').bar()" />`

In addition, it allows the corresponding expressions to get access to the arguments of the service definition using the `arg($index)` function and `args` variable inside expressions:
```yaml
services:
  foo:
    factory: '@=arg(0).baz()' # works also: @=args.get(0).baz()
    arguments: ['@bar']
```

Internally, instead of allowing `Expression` objects in `Definition` objects as in #45447, factory expressions are conveyed as a strings that starts with `@=`. This is chosen by taking inspiration from yaml and to not collide with any existing callable.

Commits
-------

c43098919c [DependencyInjection] Allow using expressions as service factories

Author: fabpot

DependencyInjection/RegisterControllerArgumentLocatorsPass.php

@@ -142,14 +142,7 @@ public function process(ContainerBuilder $container)
                         [$bindingValue, $bindingId, , $bindingType, $bindingFile] = $binding->getValues();
                         $binding->setValues([$bindingValue, $bindingId, true, $bindingType, $bindingFile]);
 
-                        if (!$bindingValue instanceof Reference) {
-                            $args[$p->name] = new Reference('.value.'.$container->hash($bindingValue));
-                            $container->register((string) $args[$p->name], 'mixed')
-                                ->setFactory('current')
-                                ->addArgument([$bindingValue]);
-                        } else {
-                            $args[$p->name] = $bindingValue;
-                        }
+                        $args[$p->name] = $bindingValue;
 
                         continue;
                     } elseif (!$autowire || (!($autowireAttributes ??= $p->getAttributes(Autowire::class)) && (!$type || '\\' !== $target[0]))) {

composer.json

@@ -28,7 +28,7 @@
         "symfony/config": "^5.4|^6.0",
         "symfony/console": "^5.4|^6.0",
         "symfony/css-selector": "^5.4|^6.0",
-        "symfony/dependency-injection": "^5.4|^6.0",
+        "symfony/dependency-injection": "^6.1",
         "symfony/dom-crawler": "^5.4|^6.0",
         "symfony/expression-language": "^5.4|^6.0",
         "symfony/finder": "^5.4|^6.0",