This is an ugly-but-simple rewrite (particularly involving having to
rewrite "single Endpoints with multiple Subsets" as "multiple
EndpointSlices"). Can be cleaned up more later...
The slice code sorts the results slightly differently from the old
code in two cases, and it was simpler to just reorder the expectations
rather than fixing the comparison code. But other than that, the
expected results are exactly the same as before.
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