### Apache Airflow version

2.2.0

### Operating System

Debian buster

### Versions of Apache Airflow Providers

_No response_

### Deployment

Astronomer

### Deployment details

astro dev start

### What happened

When I have tried to duplicate a connection first time it has created a connection with hello_copy1 and duplicating the same connection second time giving me an error of 
```Connection hello_copy2 can't be added. Integrity error, probably unique constraint.```




### What you expected to happen

It should create a connection with name hello_copy3 or the error message should be more user friendly.

### How to reproduce

https://github.com/apache/airflow/pull/15574#issuecomment-912438705

### Anything else

Suggested Error 
```
Connection hello_copy2 can't be added because it already exists.
```
or
Change the number logic in _copyN so the new name will be always unique.


### Are you willing to submit 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
'num_runs': num_runs,
            }
        )
        chart.buildcontent()
        cum_chart.buildcontent()
        s_index = cum_chart.htmlcontent.rfind('});')
        cum_chart.htmlcontent = (
            cum_chart.htmlcontent[:s_index]
            + "$( document ).trigger('chartload')"
            + cum_chart.htmlcontent[s_index:]
        )
        return self.render_template(
            'airflow/duration_chart.html',
            dag=dag,
            root=root,
            form=form,
            chart=Markup(chart.htmlcontent),
            cum_chart=Markup(cum_chart.htmlcontent),
            dag_model=dag_model,
        )
    @expose('/tries')
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    @provide_session
    def tries(self, session=None):