**Apache Airflow version**:
2.1.0

**What happened**:
There are several hooks that still use optional parameters from the classic `Extra` field.  However, when creating the connection the `Extra` field is overwritten with values from the custom fields that are included in the form.  Because the `Extra` field is overwritten, these optional parameters cannot be used by the hook.

For example, in the `AzureDataFactoryHook`, If `resource_group_name` or `factory_name` are not provided when initializing the hook, it defaults to the value specified in the connection extras. Using the Azure Data Factory connection form, here is the initial connection submission:
![image](https://user-images.githubusercontent.com/48934154/127029091-a8b1c979-f238-4bac-9d3a-f94b6cd92a2b.png)

After saving the connection, the `Extra` field is overwritten with the custom fields that use "extras" under the hood:
![image](https://user-images.githubusercontent.com/48934154/127029242-79c990f0-b9cf-43bb-9a6b-28b4e9c6d4e1.png)


**What you expected to happen**:

Wavering slightly but I would have initially expected that the `Extra` field wasn't overwritten but updated with both the custom field "extras" plus the originally configured values in the `Extra` field.  However, a better UX would be that the values used in the `Extra` field should be separate custom fields for these hooks and the `Extra` field is hidden.  Perhaps it's even both?

**How to reproduce it**:
Install either the Microsoft Azure or Snowflake providers, attempt to create a connection for either the Snowflake, Azure Data Factory, Azure Container Volume, or Azure types with the `Extra` field populated prior to saving the form.


**Anything else we need to know**:
Happy to submit PRs to fix this issue. 🚀 


airflow/www/views.py
func.count('*').label('count'),
                )
                .filter(DagRun.dag_id == dag.dag_id)
                .group_by(_convert_to_date(session, DagRun.execution_date), DagRun.state)
                .order_by(_convert_to_date(session, DagRun.execution_date).asc())
                .all()
            )
        dag_states = [
            {
                
                
                'date': dr.date if isinstance(dr.date, str) else dr.date.isoformat(),
                'state': dr.state,
                'count': dr.count,
            }
            for dr in dag_states
        ]
        data = {
            'dag_states': dag_states,
            'start_date': (dag.start_date or DateTime.utcnow()).date().isoformat(),
            'end_date': (dag.end_date or DateTime.utcnow()).date().isoformat(),
        }
        doc_md = wwwutils.wrapped_markdown(getattr(dag, 'doc_md', None))
        
        data = htmlsafe_json_dumps(data, separators=(',', ':'))
        return self.render_template(
            'airflow/calendar.html',
            dag=dag,
            doc_md=doc_md,
            data=data,