Allow bundling and execution of coreProposals upon software upgrade

[michaelfig]

What is the Problem Being Solved?

The current proposal builder architecture allows the specification of bundles, core-eval manifests, and their parameters.

These builders can be executed:

• directly by validators as part of the chain bootstrap
• by any user, to generate bundles and core-eval governance to submit to the chain

It would be useful also to enable the execution of proposal builders by validators as part of a software upgrade.

Description of the Design

1. Specify the proposal builders to execute as part of the "upgrade plan" submitted to governance. The plan is just a JSONified object, so we can add a "coreProposals": [...] property to it, using the same data structure as in our SwingSet configuration files (packages/vats/decentral-*-config.json).
2. Parse any upgrade plan information from agd's first AG_COSMOS_INIT message
3. After SwingSet initializes, use a variant of the genesis coreProposals handling to run each proposal builder and:
   a. extract the bundle entrypoint specifiers
   b. bundle the specified entrypoints
   c. controller.installBundle each of the bundles (idempotent)
   d. pass through the bundle specifiers
   e. create the core-eval scripts configured with the coreProposal options and the appropriate bundle specifiers
4. commit the swing-store so that the bundles are available for the core-evals
5. push each created core-eval action on the back of cosmic-swingset's highPriorityQueueStorage
6. return control to agd, and let normal chain scheduling promptly process the core-evals

Security Considerations

No more dangerous than genesis core-eval, and easier to audit than individual user-submitted core-evals from non-SDK sources.

Scaling Considerations

n/a

Test Plan

Test the software upgrade coreProposals via the Docker deployment upgrade test, using it to install or upgrade a new feature (such as the network and IBC vats).

Upgrade Considerations

Designed to assist upgrade.

[JimLarson]

See #7992