[8.x] When following redirects, terminate each test request in proper order

[inxilpro]

The current followRedirects() implementation applies both a while loop and recursion, causing Kernel::terminate() to be called in the incorrect order. 99% of the time this is not an issue, but in the case of terminating middleware or callbacks set up with App::terminating(), the termination callbacks will be executed in reverse order.

For example, with two routes:

Route	Middleware	Response
/from	LogRequest	Redirect to /to
/to	LogRequest	return "OK"

And the following middleware:

class LogRequest
{
    public function handle($request, $next)
    {
        return $next($request);
    }

    public function terminate($request, $response)
    {
        // Log request path and response status code
    }
}

Given the following pseudo-test:

$this->followingRedirects()->get('from');
$this->assertEquals(['from', 'to'], get_logged_request_paths()); // <-- This fails before the PR

[GrahamCampbell]

I think we should probably regard this as a breaking change, to make the behaviour better, rather than a bug fix. In which case, master is the right target branch for this.

[inxilpro]

I was originally going to submit it to master, but this is definitely a bug and the current implementation still triggers all the same code, it just does it in the incorrect order.

I'm OK submitting it for 9.x if that's your call, but I'm fairly sure that this is more a bug fix than a breaking change.