Remove ringbuffer dependency from independent periodic tasks

[Eddy Ashton (eddyashton)]

Motivation

Stacked on #8405 as the next step of the ringbuffer-removal plan. Delayed and periodic tasks, historical-state cache maintenance, and frontend endpoint maintenance currently depend on the aggregate AdminMessage::tick ringbuffer message even though they do not need the node/consensus tick's serialization.

Consensus, node-to-node channel maintenance, indexing, and the aggregate tick message remain in place for the later ordering-sensitive work.

Implementation summary

• Add a host-side libuv timer which advances the existing task clock at tick_interval. Its callback only makes due tasks runnable; task bodies still execute on task workers.
• Add PeriodicTaskOwner for weak-owner lifetime, cancellation, elapsed-time accounting, and serialization of repeated executions.
• Move historical state-cache and RPC frontend ticks to owner-managed periodic tasks. Unopened frontends continue to ignore ticks.
• Remove the unused periodic_end()/tick_end() hook.
• Preserve the existing ccf::tasks::tick() API, recurrence behavior, cancellation behavior, configured period, and deterministic fake-time tests.

Safety and compatibility

• No consensus, node-message, indexing, or ledger ordering changes. Those operations remain on the aggregate tick path.
• The historical cache already protects tick state with requests_lock; frontend ticking retains its atomic open check. Periodic callbacks hold owners weakly and are cancelled on destruction.
• The old public-recovery frontend guard protected signature emission which moved to TxHistory in 2020. History already starts its signature timer only after public recovery; current production endpoint ticks are no-ops.
• No public API, data-format, configuration, recovery, or mixed-version change.

Validation: task_system_test, historical_queries_test, frontend_test; fully linked js_generic; C++/CMake formatting, ASCII, copyright, TODO, and include-policy checks.