### 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
order_columns = [
        item for item in list_columns if item not in ['try_number', 'log_url', 'external_executor_id']
    ]
    label_columns = {
        'dag_run.execution_date': 'Execution Date',
    }
    search_columns = [
        'state',
        'dag_id',
        'task_id',
        'run_id',
        'execution_date',
        'hostname',
        'queue',
        'pool',
        'operator',
        'start_date',
        'end_date',
        'queued_dttm',
    ]
    edit_columns = [
        'state',
        'start_date',
        'end_date',
    ]
    add_exclude_columns = ["next_method", "next_kwargs", "trigger_id"]
    edit_form = TaskInstanceEditForm
    base_order = ('job_id', 'asc')
    base_filters = [['dag_id', DagEditFilter, lambda: []]]
    def log_url_formatter(self):