### 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
"""Set state to 'running'"""
        self.set_task_instance_state(tis, State.RUNNING)
        self.update_redirect()
        return redirect(self.get_redirect())
    @action('set_failed', "Set state to 'failed'", '', single=False)
    @action_has_dag_edit_access
    def action_set_failed(self, tis):
        """Set state to 'failed'"""
        self.set_task_instance_state(tis, State.FAILED)
        self.update_redirect()
        return redirect(self.get_redirect())
    @action('set_success', "Set state to 'success'", '', single=False)
    @action_has_dag_edit_access
    def action_set_success(self, tis):
        """Set state to 'success'"""
        self.set_task_instance_state(tis, State.SUCCESS)
        self.update_redirect()
        return redirect(self.get_redirect())
    @action('set_retry', "Set state to 'up_for_retry'", '', single=False)
    @action_has_dag_edit_access
    def action_set_retry(self, tis):
        """Set state to 'up_for_retry'"""
        self.set_task_instance_state(tis, State.UP_FOR_RETRY)
        self.update_redirect()
        return redirect(self.get_redirect())
class AutocompleteView(AirflowBaseView):