[HttpClient] Add a CurlClient

[adamziel]

Adds a CurlClient class to benefit from libcurl when available:

$client = Client::create();
// $client is CurlClient when libcurl extension is available and SocketClient otherwise

$client->fetch("https://w.org");

Motivateion

Curl is faster than stream_socket_* functions and supports more HTTP features (e.g. HTTP 2.0).

Implementation

Before this PR there was a single Client class that used stream_socket_* functions for managing HTTP connections.

After this PR there's:

• Client abstract class with Client::create( $options ) method.
• SocketClient – the previous Client class.
• CurlClient – the new libcurl-based HTTP client.

The event-based API remains the same. Both clients pass a similar test suite.

Testing instructions

Confirm the tests worked

[Copilot]

Pull Request Overview

This PR refactors the HTTP client by introducing a new CurlClient that leverages libcurl for improved performance and feature support, while keeping backward compatibility with the existing SocketClient. Key changes include:

• Adding the CurlClient class with a new event loop and cURL callbacks.
• Updating tests and client references to support both CurlClient and SocketClient.
• Refactoring several client usages and documentation to reflect the new design.

Reviewed Changes

Copilot reviewed 29 out of 29 changed files in this pull request and generated 3 comments.

File	Description
components/HttpClient/Tests/*	Updated tests to reference the new client classes and expected cURL error messages.
components/HttpClient/Response.php	Updated constructor signature and added header parsing improvements to support HTTP/2.0 responses.
components/HttpClient/Client/CurlClient.php	Introduced the CurlClient implementation with cURL multi-handle management and callbacks.
components/Blueprints/*	Updated type hints from Client to SocketClient to align with the client changes.