[Bug] Artifact fetcher does not honor mirrors

[turan18]

Description

The snapshotter fetches SOCI artifacts for every unique image manifest digest. We take the source information of a blob/layer, most importantly the original image reference, on the first Prepare call and create a new ORAS *remote.Repository that we use to fetch artifacts. This means that even if we had a mirror configured for a host, we would still be fetching SOCI artifacts from the original host. We should support fetching from multiple endpoints, just like we do in our span fetcher.

Steps to reproduce the bug

No response

Describe the results you expected

We could expand sociContext to include the host configurations, so that during Init we can loop through each host to try and fetch artifacts.

Host information

1. OS:
2. Snapshotter Version:
3. Containerd Version:

Any additional context or information about the bug

No response