Package versions that are accepted but not yet effective may get unvetted by unvetting automation

Noticed on DevNet validator1: we get a fight between vetting and unvetting here, leading to the same packages getting unvetted, revetted, unvetted etc.... which is in itself not smart (and all other validators are affected) and also defeats the purpose of vetting new packages early (before effective time).

Sloppy repro: https://github.com/canton-network/splice/pull/7888 ; might be a useful starting point for a proper test but please review it carefully.

Fix is probably to make unvetPackages also use associatePackageVersionsByEarliestVettingDate somehow: https://github.com/canton-network/splice/blob/bba51bb8340f68c2b385eca686e18daeb8a2ef43/apps/common/src/main/scala/org/lfdecentralizedtrust/splice/util/PackageVetting.scala#L133