Allow rules to specify and validate their options using JSON Schema

[bmish]

This would match ESLint behavior: https://eslint.org/docs/developer-guide/working-with-rules#options-schemas

This would likely be in a meta.schema property on each rule, the same as eslint, and using the same meta object that was under consideration in #943.

There are many benefits:

• No more need to write code inside rules to validate their schemas (currently done today by some of our rules in a parseConfig() function)
• Less likely to have bad data passed to rules or rules used incorrectly
• More clear exactly what rule options are supposed to look like

[rwjblue]

Seems like a good idea to me!

IMHO, this doesn't really remove the need for parseConfig conceptually, but it would make it so that it doesn't also need to validate. Specifically, it is still very useful to be able to normalize any number of valid user-land configurations into a single format that you can rely on internally in the rule (thus avoiding repeated guards or branching logic for different types of user provided config).