Change Request: One Image for all tags

[Danielku15]

As part of #375 I realized that sdk-container-builds creates a new image for every tag. I think it would be better to create only one single tar.gz with all tags set. This would:

• Reduce the load needed to generate the tar
• Reduce the load on the daemon side as only 1 docker load needs to happen
• Eliminate the problem that one application currently has N output tars.

The change should be valid from a Docker Image Specification v1.2.0 side.

[baronfel]

I agree, this would be a good change.

Separately, for the registry push code path we regenerate the entire image for each tag (this was very simple to add when it was initially done). I think we should instead push the layer and manifest blobs, and then push each separate tag blob. That would be a large performance improvement for multi-tag pushes.

[baronfel]

Closing this as @Danielku15 contributed it in dotnet/sdk#35138 for the .NET 8 release.