### 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
'conf',
    ]
    search_columns = [
        'state',
        'dag_id',
        'execution_date',
        'run_id',
        'run_type',
        'start_date',
        'end_date',
        'external_trigger',
    ]
    edit_columns = ['state', 'dag_id', 'execution_date', 'start_date', 'end_date', 'run_id', 'conf']
    base_order = ('execution_date', 'desc')
    base_filters = [['dag_id', DagEditFilter, lambda: []]]
    edit_form = DagRunEditForm
    formatters_columns = {
        'execution_date': wwwutils.datetime_f('execution_date'),
        'state': wwwutils.state_f,
        'start_date': wwwutils.datetime_f('start_date'),
        'end_date': wwwutils.datetime_f('end_date'),
        'queued_at': wwwutils.datetime_f('queued_at'),
        'dag_id': wwwutils.dag_link,
        'run_id': wwwutils.dag_run_link,
        'conf': wwwutils.json_f('conf'),
    }
    @action('muldelete', "Delete", "Are you sure you want to delete selected records?", single=False)
    @action_has_dag_edit_access
    @provide_session
    def action_muldelete(self, items, session=None):