### Description

In Airflow UI. If we go to Browse --> DAG Runs, then DAG Runs view will be displayed.

Table contains a lot of insightful values likes DAG execution date, Start date, end date, Dag config etc

Request to add DAG duration column in the same table.
DAG Duration i.e. DAG end_date timestamp  - DAG start_date timestamp

### Use case/motivation

Analytics purpose of knowing DAG duration at all DAGs level. So that I can easily find out which DAG  have least and max duration.

### Related issues

Checked open issues. There aren't any

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

airflow/www/views.py
]
        children_end_dates = [
            item['end_date'] for item in child_instances if item['run_id'] == dag_run.run_id
        ]
        children_states = [item['state'] for item in child_instances if item['run_id'] == dag_run.run_id]
        group_state = None
        for state in priority:
            if state in children_states:
                group_state = state
                break
        group_start_date = wwwutils.datetime_to_string(
            min((timezone.parse(date) for date in children_start_dates if date), default=None)
        )
        group_end_date = wwwutils.datetime_to_string(
            max((timezone.parse(date) for date in children_end_dates if date), default=None)
        )
        return {
            'task_id': task_group.group_id,
            'run_id': dag_run.run_id,
            'state': group_state,
            'start_date': group_start_date,
            'end_date': group_end_date,
        }
    group_summaries = [get_summary(dr, children) for dr in dag_runs]
    return {
        'id': task_group.group_id,
        'label': task_group.label,
        'children': children,
        'tooltip': task_group.tooltip,
        'instances': group_summaries,