[Curl] Add \r\n to HTTP status and headers to mimic what curl does

[clemherreman]

Context

When returning the array of cURL raw headers, PHP-VCR returns them like this

[
    "Content-Type: text/html; charset=UTF-8",
    "Content-Encoding: gzip",
]

However, cURL returns them more "raw", with the trailing \r\n mandatory at the end of every HTTP header line:

[
    "Content-Type: text/html; charset=UTF-8\r\n",
    "Content-Encoding: gzip\r\n",
]

This PR changes the PHP-VCR behavior. This is necessary to HTTP clients, like Symfony HTTP Client that rely on those \r\n to detect the end of the headers and the beginning of the request body, when parsing it. (or just to extract it via substr())

What has been done

VCR/Util/HttpUtil:formatHeadersForCurl() and VCR/Util/HttpUtil:formatAsStatusString() now returns a trailing \r\n to the HTTP status and HTTP header strings.

This is the actual PHP cURL behavior.

Note: This could, however be a BC change if someone was relying on not having those \r\n. However, it would then break in actual cURL requests, so I doubt that it is the case.

How to test

Unit tests were updated.