Remove runtime access from market actor state methods

[anorth]

The Runtime interface is large and dependencies on it should be restricted in order to enable testability. Ideally, access should be restricted only to top-level exported actor methods, though there are some cases where its justified to plumb a little deeper. It is often passed merely for access to the Abortf method, as an alternative to canonical Go error propagation.

The market.State object is one such place with rampant use of the Runtime only for aborting. This makes the state mutations much harder to test, and indeed they are largely untested (14% coverage).

Purge use of the runtime from this code.