Contract Upgrade: 8 PSM 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 restarting PSM contracts. (V37-V42, V73, V76)

Description of the Design

The source for the PSM contract is in [psm.js](https://github.com/Agoric/agoric-sdk/blob/master/packages/inter-protocol/src/psm/psm.js]. All the current ones are based on the code as of mainNet-1B. psm-upgrade.test.js shows that it's upgradeable.

Create a framework for a proposal to upgrade one or more contracts, and invoke it from upgrade.go. Add tests to a3p-integration.

Security Considerations

The USDT PSM contract is currently holding $300K of USDT.

Scaling Considerations

N/A.

Test Plan

Replicating the tests in psm-upgrade.test.js should be sufficient.

Upgrade Considerations

#7903 has a clean-up for the PSM contract. It should be merged before we do these upgrades.

Let's start by upgrading one of the contracts with a smaller balance, and test it on mainNet, before proceeding gradually to more substantial contracts.