User-friendly wrapper for disk imports

[wfchandler]

Overview

The Rust SDK has an extras package which abstracts away most of the complexity of importing a disk image.

It would be helpful to have a similar wrapper in the Go SDK as well.

Implementation details

No response

Anything else you would like to add?

No response

[sudomateo]

We're tackling this as part of RFD 0614.

I also wanted to note that I implemented this logic in the Omni infrastructure provider that we can use as reference: https://github.com/oxidecomputer/omni-infra-provider-oxide/blob/a53d1c9f4fdad00fe7814161cce615f20d3dbd48/internal/provider/provisioner.go#L163-L381