Expose the store objects, decycled with RefValue

[Kouteki]

Description

When exposing the store objects, use the RefValue system to handle any circular references cleanly.

By exposing these de-cycled store objects, clients (wallets, dashboards, explorers, dApps) can:

• See the full state of a contract or the chain
• Understand what's going on inside realms, packages, user accounts, etc.
• Build better tools or UIs on top of this data

[moul]

We are unsure about directly exposing the store, but we definitely want to provide an API for accessing the state.

cc @gfanton, as he is working on something similar in #2949 and is also aware of our expectations for in-gnoweb state exploration.