Fix windows image zstd compressing
What does this MR do?
In !5187 (merged) we support loading Windows helper images from zstd archives.
Unfortunately, the CI steps to achieve this were not working, so the pipeline is still loading from the registry.
Why was this MR needed?
Fixes an issue where 7z didn't support zstd archives (some 7z distributions do). Now we use the zstd utility.
What's the best way to test this MR?
Prebuilt windows job should upload zstd artifacts.