Add helper to verify liquidation parameter upgrades

[dtribble]

Description

From review of #5211:

In order for voters to be able to assure themselves that the proposed liquidation terms will perform as advertised, I think it's helpful for the subject contract (liquidateIncrementally.js) to export a helper function that validates that it would be able to parse them, and be unlikely to hiccup when restarting. Simple things like ensuring the terms parse, and the ratios have plausible known brands. Otherwise voters have to judge based on human eyes reading the textual form of the json.

Security Considerations

Fast-fail of upgrades, esp. before they are committed, is a good thing.

Test Plan

[Chris-Hibbert]

Oops. #5273 provides tools for improving liquidation parameter checking, but doesn't solve the problem.