Removing deactivated, merged, and suspended accounts from teams and subscriptions

As a Launchpad admin,
I want a process to remove deactivated, merged, and suspended persons from teams and subscriptions ,
So that the remnant data does not clutter the UI, the database, or cause oopses.

There are many bugs that relate to the non-active membership causing problems with membership and subscriptions. This should be a croned process for two reasons:
1, suspended users can be reactivated, so we must delay their unassignments for 15-30 days; 2, the merge/deactivation scripts cause UI timeouts

We may want to broaden this story to include unsubscribing the person from bugs, branches, merges, questions, and blueprints.