support_bundle_fail_expunged should not look at expunged datasets, zones

          Sorry for the drive-by comment - I don't have much context here, but I skimmed over `support_bundle_fail_expunged` and had a question. It looks like that's checking the current blueprint for _expunged_ zones/datasets specifically. How will that interact with dropping expunged entities from the blueprint altogether?

Originally posted by @jgallagher in https://github.com/oxidecomputer/omicron/pull/7063#discussion_r1906039997

support_bundle_fail_expunged could be implemented without looking at explicitly expunged datasets and zones -- it could consider the set of "all zones and datasets that are in-service", and consider anything outside of that (whether expunged, or pruned, or whatever) as "gone".

Related: I should take a look at other checks for BlueprintZoneFilter::Expunged, and see if anyone else has fallen into this expunged vs pruned issue.

Start by locating support_bundle_fail_expunged and the other checks using BlueprintZoneFilter::Expunged. Read how the current blueprint represents in-service, expunged, and pruned zones and datasets. Done means the support-bundle check treats entities outside the in-service set as gone without depending on explicitly expunged entries, and related checks have been reviewed.