[TypeDeclaration] Handle inner Closure on ReturnTypeFromReturnNewRector

[samsonasik]

Given the following code:

final class InnerClosure
{
    public function __construct()
    {
        $a = function () {
            return new \stdClass;
        };
    }
}

It currently produce parent classmethod,

-    public function __construct()
+    public function __construct(): \stdClass
     {
         $a = function () {

which invalid. This PR try to fix it.

Fixes rectorphp/rector#6858

[samsonasik]

Fixed 🎉

[samsonasik]

/cc @javaDeveloperKid

[samsonasik]

All checks have passed 🎉 @TomasVotruba it is ready for review.

[TomasVotruba]

Thank you 👍