Reindex dashboards and panels (allow migrations to queue a job to queue other indexing jobs)

Summary:
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.)

Test Plan: Ran the migration, ran bin/phd debug task, saw everything get indexed with no manual intervention.

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13272

Differential Revision: https://secure.phabricator.com/D20412