[symfony] Add 6 generic PHPStan rules (attributes, DI, return shapes)

[TomasVotruba]

Adds 6 project-agnostic rules, extracted from a real Symfony/Doctrine app where they proved useful.

Symfony

• CommandMustHaveAsCommandAttributeRule - a class extending Command must carry #[AsCommand].
• ConstraintMustHaveAttributeRule - a class extending Constraint must carry #[\Attribute], so it works as a property attribute.
• PreferInterfaceInConstructorRule - a constructor dependency typed as a concrete Symfony/Doctrine class that has a same-named *Interface should use the interface. Only 3rd-party (Symfony/Doctrine) types are checked; project classes are left alone.

General

• NoDuplicateNonRepeatableAttributeRule - an attribute repeated on the same class/method/property must declare \Attribute::IS_REPEATABLE.
• NoPropertyToPropertyAssignRule (Complexity) - $this->a = $this->b keeps the same service under 2 names; use the original directly.
• RequireArrayShapeReturnRule - a method returning a packed keyed array of 2-3 named values should declare its @return array{...} shape.

Each rule is registered in the matching config set, documented in the README, and covered by a RuleTestCase with report + skip fixtures. Console/Validator stubs added for the attribute rules.

Note: AbstractClassNameMustBeAbstractRule from the same batch was intentionally dropped - ExplicitClassPrefixSuffixRule already covers a non-abstract Abstract* class.

Green locally: ECS, PHPStan, Rector, composer-dependency-analyser, full PHPUnit (349 tests).