[CodeQuality] Skip InlineConstructorDefaultToPropertyRector on non-final class

[TomasVotruba]

Continues #8281 by @Junaid-PK (rebased on main, fixture restructured). Fixes rectorphp/rector#9837

InlineConstructorDefaultToPropertyRector moves initialization from runtime constructor flow to object creation. On a non-final class a child can omit parent::__construct() and still rely on the declared property default, so the move changes observable behavior.

Previously the rule fired on any class:

 class ValidatedBase
 {
-    private bool $validated = false;
+    private bool $validated = true;

     public function __construct()
     {
         $this->validate();
-        $this->validated = true;
     }
 }

 final class SkipsParentConstructor extends ValidatedBase
 {
     // never calls parent::__construct(), so $validated used to stay false
     public function __construct()
     {
     }
 }

Now non-final classes are left untouched; final classes are inlined as before.

The rule documentation and existing positive fixtures already use final classes, so this makes that boundary explicit.

Fixture follows the Source/ + namespaced Fixture/ convention: Source/ValidatedBase.php holds the parent, Fixture/skip_non_final_class.php.inc the non-final child that must stay unchanged.