`workers-ai-provider` not using `gateway` on REST

Despite having [the config](https://github.com/cloudflare/ai/blob/c7aa7d24480f1b62cb9ff4bd13956e1b41f44279/packages/workers-ai-provider/src/index.ts#L31C4-L47C2) for it, it never utilizes it.
Also for rest, it probably needs an optional field for `cf-aig-authorization` for REST too.