feat(node): load user actors bundle

[cryptoAtwill]

This PR load a user actor bundle into the genesis. The bundling is https://github.com/cryptoAtwill/ipc-actor-bundler. In genesis loading, it's pretty straight forward as it just needs to load the code and state cid into the store.

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Note

Adds support to load a user-actors CAR at genesis and instantiate actors from provided code/state CIDs, plumbing the bundle through the builder and tests.

• Genesis/Interpreter:
  • Add optional user_actors bundle to GenesisBuilder::new and pass to FvmGenesisState::new.
  • Parse user-actor manifest (UserActorManifest) from CAR; map actor names to code/state CIDs.
  • New FvmGenesisState methods: load_user_actor(next_actor_id) and create_actor_with_state_cid to instantiate actors from bundle.
  • Invoke state.load_user_actor(next_id) after deploying IPC contracts in populate_state.
• CLI/App:
  • Update seal_genesis to construct GenesisBuilder with the new parameter (currently None).
• Testing:
  • contract-test: include user_actors_bundle.car and pass Some(...) to create_test_genesis_state.
  • snapshot tests: adapt create_test_genesis_state calls with None.
• API Changes:
  • create_test_genesis_state signature extended to accept user_actors_bundle: Option<&[u8]>.

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