feat: allow canister_info to be invoked via query calls

[mraszyk]

The management canister method canister_info can now be invoked via non-replicated (query) calls by external users and from composite query methods, in addition to inter-canister calls. It remains rejected for ingress messages. Retrieving canister information is not subject to any access control.

[mraszyk]

Feedback addressed:

• abstract-behavior.md: added A.canister_id ∈ dom(S.canisters) to the conditions of the replicated canister_info rule. It is needed: since canister_info has no access control, nothing else constrained A.canister_id, so the state-after could reference S.canister_history[A.canister_id], S.canisters[A.canister_id] and S.controllers[A.canister_id] for a non-existent canister. This also matches the query-call rule and management_canister_query added in this PR, and provisional_top_up_canister, the other rule without access control, which already carries the same condition.
• management-canister.md: added canister_metadata to the list of methods never accepted as ingress messages. The list was already inconsistent with the canister_metadata section itself, which states the method cannot be called by external users via ingress messages.
• Changelog date: already updated to 2026-08-31 in 2a55a71.

Heads up: PR #252 also adds a 0.67.0 changelog section, so whichever of the two lands second will need its version bumped to 0.68.0.