io.containerd.image.name annotation using docker.io

In https://github.com/dotnet/sdk/pull/46467 `io.containerd.image.name` was introduced:

https://github.com/dotnet/sdk/blob/270865c5d3d434bdf4faa2ee096fbb3cae896117/src/Containers/Microsoft.NET.Build.Containers/ImageIndexGenerator.cs#L108

Currently this is hard coded to `docker.io`:

https://github.com/dotnet/sdk/blob/270865c5d3d434bdf4faa2ee096fbb3cae896117/src/Containers/Microsoft.NET.Build.Containers/ImageIndexGenerator.cs#L95

I wonder if this shouldn't be using the registry that is being pushed to?

I unexpectedly saw this `docker.io` prefix show up when I did the following:
```
dotnet publish /t:PublishContainer /p:ContainerBaseImage=registry.access.redhat.com/ubi8/dotnet-90-runtime /p:ContainerRepository=app /p:ContainerArchiveOutputPath=app-image.tar -v d
podman load -i app-image.tar
```

Podman then says:
```
Loaded image: docker.io/library/app:latest
```

@dotnet/sdk-container-builds-maintainers ptal.

Start with src/Containers/Microsoft.NET.Build.Containers/ImageIndexGenerator.cs around lines 95 and 108, then reproduce the issue with the dotnet publish and podman load commands in the report. Trace how the target registry is represented and verify that the generated image annotation and loaded image name use it instead of a hard-coded docker.io value.

Written by the indexing model from the issue text.