Actor heartbeat timer

[yue-fred-gao]

ha-scope actor requires a maintenance timer like once per hour. Each time the timer fires, we need to update last_heartbeat_time_in_ms in NPU state_db DASH_HA_SCOPE_STATE.

Proposal: create an actor that sends swbus message to registered actor at specified interval. ha-scope actor receives the message and update the last_heartbeat_time_in_ms.