Implement data source component

[sudomateo]

Implement a data source component to fetch an image ID from the Oxide API. There may be other data source components created in the future but this one is a good way to start development on the Oxide Packer plugin since it's read-only and doesn't require a ton of testing infrastructure to move forward.

When finished a user should be able to use the data source component like so.

data "oxide-image" "example" {
    name = "ubuntu-24-04"
}

locals {
    image_id = data.oxide-image.example.image_id
}