Add airflowctl tasks state command - #71206

This adds airflowctl tasks state, which prints the state of a single task instance. It is the airflowctl equivalent of the deprecated airflow tasks state.

You select the run with either a run id or a logical date, and mapped tasks are supported through --map-index:

  airflowctl tasks state <dag_id> <task_id> <run_id>
  airflowctl tasks state <dag_id> <task_id> --logical-date <logical_date>

The output is just the state value (for example success) to stay script friendly. It reuses the existing task instance API operation, and error handling matches the sibling failed-deps and states-for-dag-run commands.

closes: #6617