fix(compartment-mapper): fix ReadPowers-related types

[boneskull]

Description

This change:

1. Creates a minimal interface for the fs, url, and crypto objects as passed into makeReadPowers(). This makes it easier to duck-type the objects. The drawback here is that it is not future-proof, and these types will need to be updated if we end up using additional methods on these objects.
2. Fixes the invalid type of MaybeReadPowers; properties (defined thru @property) are ignored in a @typedef of that @typedef does not extend object/Object.
3. Added necessary type assertion in powers.js
4. Adds return type to makeReadPowersSloppy()

Upgrade Considerations

This is a type-only change.

[boneskull]

• #2190
• #2189
• #2188 👈
• master

This stack of pull requests is managed by Graphite. Learn more about stacking.

Join @boneskull and the rest of your teammates on Graphite