fix(instance): let the backend resolve marketplace images

[aslafy-z]

Remove the client side marketplace image resolution from the CreateServer method.
It's already done at backend level: https://www.scaleway.com/en/developers/api/instance/#path-instances-create-an-instance.

Instance image ID or label. When an image label is used, it will be converted to the latest image available on the Marketplace. By default, the selected local image will be the instance_sbs local image. If an l_ssd volume is specified in the volumes argument, an instance_local local image will be selected instead.

Currently, this code does not resolve conditionally depending on server volumes.

This update mimics the Console behavior, making the backend responsible from selecting the marketplace image.

Fixes #2603