Use host_id in a children list of a task in task manager to indicate
a node on which the child was created.
Move TASKS_CHILDREN_REQUEST to IDL. Send it by host_id.
Fixes: https://github.com/scylladb/scylladb/issues/22284.
Ip to host_id transition; backport isn't needed.
Closesscylladb/scylladb#22487
* github.com:scylladb/scylladb:
tasks: drop task_manager::config::broadcast_address as it's unused
tasks: replace ip with host_id in task_identity
api: task_manager: pass gossiper to api::set_task_manager
tasks: keep host_id in task_manager
tasks: move tasks_get_children to IDL