Depends on D20411. Ref T13272. Dashboards and panels have new indexes (Ferret and usage edges) that need a rebuild.
For large datasets like commits we have the "activity" flow in T11932, but realistically these rebuilds won't take more than a few minutes on any realistic install so we should be able to just queue them up as migrations.
Let migrations insert a job to basically run bin/search index --type SomeObjectType, then do that for dashboards and panels.
(I'll do Herald rules in a followup too, but I want to tweak one indexing thing there.)