[PHPUnit60] Add DoesNotPerformAssertions attribute directly and skip traits

[TomasVotruba]

Two changes to AddDoesNotPerformAssertionToNonAssertingTestRector:

1) Add the attribute directly, when it exists

If PHPUnit\Framework\Attributes\DoesNotPerformAssertions is available (PHPUnit 10+), the attribute is added instead of the annotation. Projects on older PHPUnit keep getting the docblock annotation.

 final class SomeTest extends TestCase
 {
-    public function test()
+    #[\PHPUnit\Framework\Attributes\DoesNotPerformAssertions]
+    public function test()
     {
         $nothing = 5;
     }
 }

Previously this always produced:

    /**
     * @doesNotPerformAssertions
     */

2) Skip traits

A trait method has no owning class, so there is no way to tell whether the class using it asserts elsewhere. Adding the attribute there can silence a real assertion check.

trait SomeNonAssertingTrait
{
    // left as is
    public function testSomething()
    {
        $nothing = 5;
    }
}