refactor: Bundle SystemMetadata subnet fields into OwnSubnetInfo struct

[alin-at-dfinity]

Bundle SystemMetadata fields own_subnet_features, own_resource_limits and node_public_keys into an OwnSubnetInfo struct, in preparation for easy reuse across ReplicatedStates when using the same registry version.

[zeropath-ai]

✅ No security or compliance issues detected. Reviewed everything up to 4b3050a.

Security Overview

• 🔎 Scanned files: 21 changed file(s)
• 🔗 Scan Link: https://zeropath.com/app/repositories/f5e9d2bb-29a4-4b64-902a-391d65fd8b2d?scanId=1a5ea1cc-f061-44c1-9ad7-fb48296e932d&codeScanTypes=PrScan&tab=issues

Detected Code Changes

Change Type	Relevant files
Enhancement	► rs/canonical_state/src/lazy_tree_conversion.rs     Use own_subnet_info.node_public_keys instead of node_public_keys
Enhancement	► rs/canonical_state/src/traversal.rs     Modify test to update own_subnet_info.node_public_keys via Arc::make_mut
Enhancement	► rs/execution_environment/src/execution_environment.rs     Switch from own_subnet_features.http_requests to state.subnet_features().http_requests
Enhancement	► rs/execution_environment/src/execution_environment/tests.rs     Update tests to mutate own_subnet_info.subnet_features.http_requests via Arc::make_mut
Enhancement	► rs/execution_environment/src/scheduler/tests/metrics.rs     Update tests to mutate own_subnet_info.subnet_features.http_requests via Arc::make_mut
Enhancement	► rs/messaging/src/message_routing.rs     Replace returned tuple types to use OwnSubnetInfo; update read_registry/read flow accordingly
Enhancement	► rs/messaging/src/state_machine.rs     Adapt StateMachine trait and implementation to use OwnSubnetInfo; remove direct node_public_keys usage
Enhancement	► rs/messaging/src/state_machine/tests.rs     Update tests to pass OwnSubnetInfo instead of separate subnet_features/resource_limits/node_public_keys
Enhancement	► rs/protobuf/def/state/metadata/v1/metadata.proto     Add OwnSubnetInfo message and own_subnet_info field; deprecate direct fields
Enhancement	► rs/protobuf/src/gen/state/state.metadata.v1.rs     Add OwnSubnetInfo struct; adjust SystemMetadata to hold own_subnet_info instead of individual fields
Enhancement	► rs/replicated_state/src/lib.rs     Expose OwnSubnetInfo in public API instead of separate fields
Enhancement	► rs/replicated_state/src/metadata_state.rs     Replace own_subnet_features/own_resource_limits/node_public_keys with own_subnet_info: Arc
Enhancement	► rs/replicated_state/src/replicated_state.rs     Add subnet_features()/resource_limits() accessors delegating to own_subnet_info
Enhancement	► rs/state_manager/src/tree_hash.rs     Initialize node_public_keys via own_subnet_info in tests
Enhancement	► rs/state_manager/tests/state_manager.rs     Mutate node_public_keys via own_subnet_info in tests
Enhancement	► rs/test_utilities/execution_environment/src/lib.rs     Prepare and mutate own_subnet_info for subnet_features adjustments
Enhancement	► rs/test_utilities/state/src/lib.rs     Mutate own_subnet_info.subnet_features instead of direct field
Enhancement	► rs/replicated_state/src/metadata_state/proto.rs     Implement From/TryFrom for OwnSubnetInfo; adjust serialization to reflect new structure
Enhancement	► rs/replicated_state/src/metadata_state/proto.rs     Handle backward-compatibility for missing own_subnet_info when reading older checkpoints