The Windows Server Core images are quite large (~2GB each), and pulling
it for multiple build jobs / E2E images is inefficient, especially if
have to build for multiple OS versions.
The windows-servercore-cache image is meant to simply cache the Windows files
we need from the Windows Server core images, so we can pull the small cache image
instead of the entire image. It is never meant to be a promotable image,
the version is not meant to be bumped.
The other images (e.g.: agnhost) rely on the version 1.0 images.
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