[5.8] Prevent TestRespone dump methods from ending execution of the script

[d3jn]

Greetings!

This is something that has been bothering me for quite some time so I propose a change. TestResponse::dump() and TestResponse::dumpHeaders() methods actually use dd() helper (instead of dump()) thus killing the execution of the script.

Not only is this counter-intuitive, but also should be classified as a bug because it goes against the examples official documentation provides:

    public function testBasicTest()
    {
        $response = $this->get('/');

        $response->dumpHeaders();

        $response->dump();
    }

The way it's currently implemented this example from the docs won't even work properly, because only headers will be dumped and then the execution of the script will be halted. Making TestResponse dump methods to actually dump things like dump() does would drastically improve tests' debugging experience out of the box (for now I've been registering realDump macro for TestResponse in my projects which is inconvenient).

For those, who want previous behavior we can also discuss introducing dd() and ddHeaders() methods to TestResponse class.