[php-src] PR #22970: Parse qualified reflection names with a length-aware search

Pull Request: https://github.com/php/php-src/pull/22970 Author: iliaal ReflectionMethod::__construct(), ReflectionMethod::createFromMethodName() and ReflectionClass::getProperty() split a Class::member argument with strstr(), which stops at the first NUL byte. Anonymous class names embed one, so a name that ReflectionClass::getName() just handed back is rejected. zend_memnstr() searches the declared length instead. ```php $obj = new class { public function m() {} }; $name = (new ReflectionClass($obj))->getName(); ReflectionMethod::createFromMethodName($name . '::m'); // ReflectionException: Argument #1 ($objectOrMethod) must be a valid method name ``` These are the same two lines #22922 rewrites to fix the NUL truncation in the exception messages, so one of the two will need a rebase.