This test was removed because package sets in chains are no longer
visible in the map returned from ImageType.PackageSets().
Bringing back the test now to ensure that:
1. All package set names defined in the keys returned from the
PackageSets() map match the keys returned from the
PackageSetsChains() map.
2. All package sets defined in the package set chains are defined for
the image type. This is tested by the function PackageSets()
function itself, which should never panic.
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