fix #10564: include wells in plate run processing

When processing a plate run, also process its wells.

Fixes https://trac.openmicroscopy.org.uk/ome/ticket/10564

To test, try deleting the last plate run of a plate that another user owns and that you have permission to delete. Then, try double-clicking on the plate in Insight and see if the data browser shows thumbnail weirdness.

Also, make sure that `AdminServiceTest` and `HierarchyDeleteTest` are still both passing; in the latter, `testDeletingMultipleRunsWithOrphanedSamples` verifies https://github.com/openmicroscopy/openmicroscopy/pull/1430#issuecomment-25079034.