Support function as virtual/durable kinds

[mhofman]

What is the Problem Being Solved?

Today Far accepts either a function or an object (with methods). However the same support for exportable functions is not extended to virtual / durable kinds.

Description of the Design

Accept a function as behavior for a single facet kind, and as facets for a multi kind.

Update zones to make sure function behaviors are accepted (probably update types as well).

Consider having the exo makers be virtual/durable as well, as least for durable zones so they can be stored (for async-flow endowments)

Figure out if this simplifies any of the Callback stuff.

Security Considerations

None. Having makers be themselves virtual/durable would make them exportable, which may not be expected.

Scaling Considerations

None

Test Plan

TBD

Upgrade Considerations

Requires an upgrade to liveslots, which is only deployed as part of chain software upgrades.

This is technically enables functionality that was previously failing, so a contract using this feature would need to be deployed on an updated liveslots versions. We don't currently have a mechanism to verify/assert "expected features".