### 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
"""Formats hidden fields"""
        key = self.get('key')
        val = self.get('val')
        if secrets_masker.should_hide_value_for_key(key):
            return Markup('*' * 8)
        if val:
            return val
        else:
            return Markup('<span class="label label-danger">Invalid</span>')
    formatters_columns = {
        'val': hidden_field_formatter,
    }
    validators_columns = {'key': [validators.DataRequired()]}
    def prefill_form(self, form, request_id):