Fix swapped preCondition and postCondition attribute mapping

[TomasVotruba]

@preCondition was converted to #[PostCondition] and @postCondition to #[PreCondition] - the two mappings are swapped, so the hooks end up running at the wrong point of the test lifecycle.

-        new AnnotationToAttribute('preCondition', 'PHPUnit\Framework\Attributes\PostCondition'),
-        new AnnotationToAttribute('postCondition', 'PHPUnit\Framework\Attributes\PreCondition'),
+        new AnnotationToAttribute('preCondition', 'PHPUnit\Framework\Attributes\PreCondition'),
+        new AnnotationToAttribute('postCondition', 'PHPUnit\Framework\Attributes\PostCondition'),

Before:

/**
 * @preCondition
 */
protected function setUpSomething()
{
}

was turned into:

#[\PHPUnit\Framework\Attributes\PostCondition]
protected function setUpSomething()
{
}

There was no fixture covering these two annotations, which is how the swap went unnoticed. Added pre_post_condition.php.inc.