Contract upgrade: governance contracts

[Chris-Hibbert]

What is the Problem Being Solved?

As mentioned in #8158, we need the ability to restart all vats. This issue is concerned with upgrading the contract governors.

Description of the Design

Contract Governors are built from contractGovernor.js.

We were able to null upgrade vaultFactory-governor in U16-VA, which shows governor vats are safely upgradeable. There's no value in upgrading governors for contracts (like auctions) that will be replaced rather than upgraded.

Security Considerations

no special considerations

Scaling Considerations

not a scaling concern.

Test Plan

We've demonstrated that it works in general, so we only need a3p tests that the proposal is upgrading the intended thing.

Upgrade Considerations

see above.