Currently, node ops virtual task gathers its children from all nodes contained
in a sum of service::topology::normal_nodes and service::topology::transition_nodes.
The maps may contain nodes that are down but weren't removed yet. So, if a user
requests the status of a node ops virtual task, the task's attempt to retrieve
its children list may fail with seastar::rpc::closed_error.
Filter out the tasks that are down in node_ops::task_manager_module::get_nodes.
Fixes: #20843.
(cherry picked from commit a558abeba3)
Closesscylladb/scylladb#20898
system_keyspace::get_topology_request_entries returns entries for
requests which are running or have finished after specified time.
In task manager node ops task set the time so that they are shown
for task_ttl seconds after they have finished.
Add topology_tasks test suite for testing task manager's node ops
tasks. Add TaskManagerClient to topology_tasks for an easy usage
of task manager rest api.
Write a test for bootstrap, replace, rebuild, decommission and remove
top level tasks using the above.
