✨ Add proxy_http_fetch method to the SDK

[Thomasvdam]

✨ Feature

As part of the data proxy feature of the SEDA network the overlay nodes will need to support a new method proxy_http_fetch (name not final) in order to be able to query authenticated APIs.

Motivation

Help developers easily build DR WASMs that query authenticated APIs.

Implementation

• Implement proxy_http_fetch in the AS SDK.
• Add support for proxy_http_fetch in the test VM adapters.
• Check whether any additional helpers are needed to write unit tests.'

Related Issues

Somewhat related to https://github.com/sedaprotocol/seda-overlay/issues/177 as it'll need to mimick the actual interface.

[Thomasvdam]

Partially closed by #70 and the remainder will be picked up in #71