tweak(server/http): provide error response headers

[D4isDAVID]

Goal of this PR

In the source code, an HTTP request failure is both failure to connect, but also response codes such as 4xx or 5xx. In both cases, response headers are not provided to scripts.

The problem is that when HTTP servers respond with an error code such as 4xx or 5xx, they may also provide response headers which may contain valuable information - such as the Discord API providing rate limit information when getting rate limited.

The goal is to provide those response headers when requests fail.

How is this PR achieving the goal

Always creates the response data, not only when the request is successful, and passes it to the callback event also when the request has failed.

Seeing as this may be constituted as a breaking change, I passed it as a new callback parameter instead of the existing headers parameter.

This PR applies to the following area(s)

Server, ScRT: Lua

Successfully tested on

Platforms: Windows

Checklist

• Code compiles and has been tested successfully.
• Code explains itself well and/or is documented.
• My commit message explains what the changes do and what they are for.
• No extra compilation warnings are added by these changes.