### 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
priority = [
            'failed',
            'upstream_failed',
            'up_for_retry',
            'up_for_reschedule',
            'queued',
            'scheduled',
            'deferred',
            'sensing',
            'running',
            'shutdown',
            'restarting',
            'removed',
            'no_status',
            'success',
            'skipped',
        ]
        child_instances = [child['instances'] for child in children if 'instances' in child]
        child_instances = [item for sublist in child_instances for item in sublist]
        children_start_dates = [
            item['start_date'] for item in child_instances if item['run_id'] == dag_run.run_id