compartment-mapper: add policy types

[boneskull]

What is the Problem Being Solved?

Policies are essentially untyped (considered to be arbitrary objects). It would be helpful for consumers to have access to type information so that they do not construct invalid policies.

Description of the Design

A policy has a shape defined already; it's just a matter of formalizing that shape into types.

Security Considerations

none

Scaling Considerations

none

Test Plan

I'd probably want to add tsd tests for this; while it looks like tsd is used in other workspaces, I'll need to add the tsd package to compartment-mapper.

Upgrade Considerations

[dckc]

See also:

• https://github.com/Agoric/agoric-sdk/issues/6160