Remove extra params wrapper for network_interfaces in instance create api

[just-be-dev]

I've been working through wiring up the UI to the instance create api and I ran across a relatively strange paradigm. When adding a network interface to the instance create endpoint it required a nested params key that made the api awkward.

Here's a rough example of what it'd look like in the post body.

{
  network_interfaces: {
    type: "Create",
    params: {
      params: {
        ...NetworkInterfaceParams
      }
    }
  }
}

So far as I can tell the InstanceNetworkInterfaceCreate isn't actually necessary but I could be missing some future intent here.

[david-crespo]

into it

[bnaecker]

Looks good thanks! This was a holdover I believe from when I thought we might add the ability to attach to an existing interface. Thanks for the cleanup.