[12.x] Add ddBody method to TestResponse for dumping various response payloads

[Sammyjo20]

This PR implements a more generic ddBody method to the Illuminate/Testing/TestResponse class which is useful for dumping out any HTTP response body.

The ddJson method was added previously and this code will use that if json_validate passes. Otherwise it will dump out the content of the response.

I noticed there weren't any tests for the other methods so I didn't write a test for this, however happy to write tests for this if needed.

---

Q: Do we need to do anything with streamed content? I noticed the following code in the codebase, perhaps we should use getStreamedContent() when the response is streamed?

if ($this->baseResponse instanceof StreamedResponse ||
    $this->baseResponse instanceof StreamedJsonResponse) {
    // $this->streamedContent();
} else {
    // $this->getContent();
}

[mohammadrasoulasghari]

I think this condition should probably also be added to ddJson, if json_validate is strictly required.

[Sammyjo20]

@taylorotwell Sorry for the @ mention directly - but I just had a thought - will this break Laravel for people using PHP 8.2? I forgot to check what the minimum version was and it looks like it's ^8.2.

[Sammyjo20]

Perhaps it just needs to change to

if (function_exists('json_validate') && json_validate($content)) {
   $this->ddJson($key);
}

[Sammyjo20]

I've created a PR if you choose to merge this.