feat: Add a cooling_down field to SubnetRecord

[mraszyk]

The field can be set via UpdateSubnetRecord governance proposals (the engine controller is deliberately kept out of scope: it may only set subnet_admins and is_halted) and is now read into SubnetTopology::cooling_down, which used to be hardcoded to false because no registry field was backing it.

The field must not be set in prod until #11117, which introduced the new error code for ingress messages rejected on cooling down subnets (ErrorCode::SubnetCoolingDown), is rolled out to all subnets on mainnet.

[github-actions]

This pull request changes code owned by the Governance team. Therefore, make sure that
you have considered the following (for Governance-owned code):

1. Update unreleased_changelog.md (if there are behavior changes, even if they are
   non-breaking).

2. Are there BREAKING changes?

3. Is a data migration needed?

4. Security review?

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• $REASON_WHY_NO_NEED. E.g. for unreleased_changelog.md, "No
  canister behavior changes.", or for item 2, "Existing APIs
  behave as before.".

Brief Guide to "Externally Visible" Changes

"Externally visible behavior change" is very often due to some NEW canister API.

Changes to EXISTING APIs are more likely to be "breaking".

If these changes are breaking, make sure that clients know how to migrate, how to
maintain their continuity of operations.

If your changes are behind a feature flag, then, do NOT add entrie(s) to
unreleased_changelog.md in this PR! But rather, add entrie(s) later, in the PR
that enables these changes in production.

Reference(s)

For a more comprehensive checklist, see here.

GOVERNANCE_CHECKLIST_REMINDER_DEDUP

[zeropath-ai]

✅ No security or compliance issues detected. Reviewed everything up to d00beed.

Security Overview

• 🔎 Scanned files: 31 changed file(s)
• 🔗 Scan Link: https://zeropath.com/app/repositories/6992424c-495e-4621-b441-efd6821a4be6?scanId=55f4be73-c7ef-49f4-823c-bafd802f00d3&codeScanTypes=PrScan&tab=issues

Detected Code Changes

Change Type	Relevant files
Enhancement	► rs/boundary_node/ic_boundary/src/test_utils.rs     Add cooling_down field to SubnetRecord construction ► rs/crypto/temp_crypto/src/lib.rs     Add cooling_down to EcdsaSubnetConfig initialization ► rs/engine_controller/canister/canister.rs     Include cooling_down in ensure_only_allowed_fields_set payload checks
Enhancement	► rs/engine_controller/canister/tests.rs     Include cooling_down in test payloads
Enhancement	► rs/engine_controller/engine_controller.did     Add cooling_down field to UpdateSubnetPayload type
Enhancement	► rs/engine_controller/unreleased_changelog.md     Document cooling_down field in update_subnet behavior
Enhancement	► rs/messaging/src/message_routing.rs     Propagate cooling_down from subnet_record when available
Enhancement	► rs/nns/integration_tests/src/subnet_handler.rs     Initialize cooling_down in test payloads and updates
Enhancement	► rs/orchestrator/registry_replicator/src/internal_state.rs     Set default cooling_down in test state
Enhancement	► rs/prep/src/subnet_configuration.rs     Initialize cooling_down in subnet config
Enhancement	► rs/protobuf/def/registry/subnet/v1/subnet.proto     Add cooling_down field to SubnetRecord (bool, tag 35)
Enhancement	► rs/protobuf/src/gen/registry/registry.subnet.v1.rs     Add cooling_down field to SubnetRecord (bool, tag 35)
Enhancement	► rs/protobuf/src/gen/state/registry.subnet.v1.rs     Add cooling_down field to SubnetRecord (bool, tag 35)
Enhancement	► rs/protobuf/src/gen/types/registry.subnet.v1.rs     Add cooling_down field to SubnetRecord (bool, tag 35)
Enhancement	► rs/registry/admin/bin/types.rs     Add cooling_down field to SubnetRecord struct and From conversion ► rs/registry/admin/bin/update_subnet.rs     Add cooling_down to command and payload and propagate in update
Enhancement	► rs/registry/canister/canister/registry.did     Add cooling_down to SubnetRecord and UpdateSubnetPayload definitions
Enhancement	► rs/registry/canister/canister/registry_test.did     Add cooling_down to SubnetRecord and UpdateSubnetPayload
Enhancement	► rs/registry/canister/src/get_subnet.rs     Include cooling_down in SubnetRecord retrieval
Enhancement	► rs/registry/canister/src/mutations/do_create_subnet.rs     Initialize cooling_down in new SubnetRecord
Enhancement	► rs/registry/canister/src/mutations/do_split_subnet.rs     Initialize cooling_down in new SubnetRecord during split
Enhancement	► rs/registry/canister/src/mutations/do_update_subnet.rs     Handle cooling_down in payload scope, merge, and tests
Enhancement	► rs/registry/canister/tests/update_subnet.rs     Add cooling_down to test payloads and assertions
Enhancement	► rs/registry/canister/tests/update_subnet_admins.rs     Add cooling_down to test payloads in various scenarios
Enhancement	► rs/registry/canister/unreleased_changelog.md     Document cooling_down behavior and rollout considerations
Enhancement	► rs/test_utilities/registry/src/lib.rs     Add cooling_down to test SubnetRecord construction
Enhancement	► rs/tests/consensus/cup_explorer_test.rs     Set cooling_down: None in UpdateSubnetPayload for test
Enhancement	► rs/tests/consensus/tecdsa/utils/src/lib.rs     Add cooling_down: None to empty subnet update
Enhancement	► rs/tests/consensus/utils/src/ssh_access.rs     Add cooling_down: None to update subnet payload helper
Enhancement	► rs/tests/message_routing/xnet/subnet_delete_test.rs     Add cooling_down: None in test payloads
Enhancement	► rs/tests/testnets/mainnet_nns/src/lib.rs     Add cooling_down: None in test setup payloads

[zeropath-ai]

✅ No security or compliance issues detected. Reviewed everything up to d00beed.

Security Overview

• 🔎 Scanned files: 31 changed file(s)
• 🔗 Scan Link: https://zeropath.com/app/repositories/f5e9d2bb-29a4-4b64-902a-391d65fd8b2d?scanId=a0d25946-3964-49ca-a038-d0b12c63b569&codeScanTypes=PrScan&tab=issues

Detected Code Changes

Change Type	Relevant files
Enhancement	► rs/boundary_node/ic_boundary/src/test_utils.rs     Add cooling_down field to SubnetRecord construction ► rs/crypto/temp_crypto/src/lib.rs     Add cooling_down to EcdsaSubnetConfig initialization ► rs/engine_controller/canister/canister.rs     Include cooling_down in ensure_only_allowed_fields_set payload checks
Enhancement	► rs/engine_controller/canister/tests.rs     Include cooling_down in test payloads
Enhancement	► rs/engine_controller/engine_controller.did     Add cooling_down field to UpdateSubnetPayload type
Enhancement	► rs/engine_controller/unreleased_changelog.md     Document cooling_down field in update_subnet behavior
Enhancement	► rs/messaging/src/message_routing.rs     Propagate cooling_down from subnet_record when available
Enhancement	► rs/nns/integration_tests/src/subnet_handler.rs     Initialize cooling_down in test payloads and updates
Enhancement	► rs/orchestrator/registry_replicator/src/internal_state.rs     Set default cooling_down in test state
Enhancement	► rs/prep/src/subnet_configuration.rs     Initialize cooling_down in subnet config
Enhancement	► rs/protobuf/def/registry/subnet/v1/subnet.proto     Add cooling_down field to SubnetRecord (bool, tag 35)
Enhancement	► rs/protobuf/src/gen/registry/registry.subnet.v1.rs     Add cooling_down field to SubnetRecord (bool, tag 35)
Enhancement	► rs/protobuf/src/gen/state/registry.subnet.v1.rs     Add cooling_down field to SubnetRecord (bool, tag 35)
Enhancement	► rs/protobuf/src/gen/types/registry.subnet.v1.rs     Add cooling_down field to SubnetRecord (bool, tag 35)
Enhancement	► rs/registry/admin/bin/types.rs     Add cooling_down field to SubnetRecord struct and From conversion ► rs/registry/admin/bin/update_subnet.rs     Add cooling_down to command and payload and propagate in update
Enhancement	► rs/registry/canister/canister/registry.did     Add cooling_down to SubnetRecord and UpdateSubnetPayload definitions
Enhancement	► rs/registry/canister/canister/registry_test.did     Add cooling_down to SubnetRecord and UpdateSubnetPayload
Enhancement	► rs/registry/canister/src/get_subnet.rs     Include cooling_down in SubnetRecord retrieval
Enhancement	► rs/registry/canister/src/mutations/do_create_subnet.rs     Initialize cooling_down in new SubnetRecord
Enhancement	► rs/registry/canister/src/mutations/do_split_subnet.rs     Initialize cooling_down in new SubnetRecord during split
Enhancement	► rs/registry/canister/src/mutations/do_update_subnet.rs     Handle cooling_down in payload scope, merge, and tests
Enhancement	► rs/registry/canister/tests/update_subnet.rs     Add cooling_down to test payloads and assertions
Enhancement	► rs/registry/canister/tests/update_subnet_admins.rs     Add cooling_down to test payloads in various scenarios
Enhancement	► rs/registry/canister/unreleased_changelog.md     Document cooling_down behavior and rollout considerations
Enhancement	► rs/test_utilities/registry/src/lib.rs     Add cooling_down to test SubnetRecord construction
Enhancement	► rs/tests/consensus/cup_explorer_test.rs     Set cooling_down: None in UpdateSubnetPayload for test
Enhancement	► rs/tests/consensus/tecdsa/utils/src/lib.rs     Add cooling_down: None to empty subnet update
Enhancement	► rs/tests/consensus/utils/src/ssh_access.rs     Add cooling_down: None to update subnet payload helper
Enhancement	► rs/tests/message_routing/xnet/subnet_delete_test.rs     Add cooling_down: None in test payloads
Enhancement	► rs/tests/testnets/mainnet_nns/src/lib.rs     Add cooling_down: None in test setup payloads

Done