make governance system allow governed contracts to be upgradable

[turadg]

What is the Problem Being Solved?

All contracts after bulldozer have to be upgradable. We've decided that none of the governance state is precious (because it's all published publicly) so we don't need durable storage:

• use Durable objects for governance #5200

Moreover, the security assurances of governance may be violated by passing baggage through to handleGovernance of the governed contract.

Description of the Design

The contracts are upgradable and have some some way to restore the governance state.

Security Considerations

Scaling Considerations

Test Plan

A swingset or bootstrap test that upgrades a governed contract