[TypeDeclaration] Handle union A extends B on ReturnUnionTypeRector

[samsonasik]

Cherry picked from PR:

• [PHPStanStaticTypeMapper] Early uniquate types check on UnionTypeMapper to clean up manual check #5148

due to clean up manual check on UnionTypeMapper, that I found a bug on it.

[samsonasik]

It seems cause a bug on AddMethodCallBasedStrictParamTypeRector

There were 2 failures:

1) Rector\Tests\TypeDeclaration\Rector\ClassMethod\AddMethodCallBasedStrictParamTypeRector\UnionTest::test with data set #1
Failed on fixture file "narrow_union.php.inc"
Failed asserting that string matches format description.
--- Expected
+++ Actual
@@ @@
         $this->someExpr($string);
     }
 
-    private function someExpr(\PhpParser\Node\Expr\MethodCall|\PhpParser\Node\Expr\StaticCall|\PhpParser\Node\Scalar\String_ $expr)
+    private function someExpr(\PhpParser\Node\Expr $expr)

I will check more.

[samsonasik]

Fixed 🎉

[samsonasik]

All checks have passed 🎉 @TomasVotruba I think it is ready.

[TomasVotruba]

Looks good to me, thanks 👍