### Apache Airflow version

2.2.0 (latest released)

### Operating System

Ubuntu

### Versions of Apache Airflow Providers

_No response_

### Deployment

Other

### Deployment details

Just used `airflow standalone`

### What happened

First:

TaskGroup does not show the tooltip that is defined for that group on hover
![2021-10-19_17h00_18](https://user-images.githubusercontent.com/35238779/137937706-376922b8-2f79-47ac-9789-6007d135f855.png)

Second:

Providing an Operator with `task_group=` instead of TaskGroup as context manager ignores that TaskGroup's default_args. Using the code I provided below, the task "end" in section_3 has the wrong owner.


### What you expected to happen

First:

If a TaskGroup is used and the tooltip is defined like so:
```python
with TaskGroup("section_1", tooltip="Tasks for section_1") as section_1:
```
the information provided with`tooltip="..."` should show on hover, as shown in the official documentation at https://airflow.apache.org/docs/apache-airflow/stable/concepts/dags.html#taskgroups


Second:

Defining a TaskGroup with default_args like
```python
section_3 = TaskGroup("section_3", tooltip="Tasks for section_2", default_args={"owner": "bug"})
```
should result in those default_args being used by tasks defined like so:
```python
end = DummyOperator(task_id="end", task_group=section_3)
```

### How to reproduce

I have tested this with the below code

```python
from datetime import datetime

from airflow.models.dag import DAG
from airflow.operators.bash import BashOperator
from airflow.operators.dummy import DummyOperator
from airflow.utils.task_group import TaskGroup

with DAG(
    dag_id="task_group_test",
    start_date=datetime(2021, 1, 1),
    catchup=False,
    tags=["example"],
    default_args={"owner": "test"},
) as dag:
    start = DummyOperator(task_id="start")

    with TaskGroup("section_1", tooltip="Tasks for section_1") as section_1:
        task_1 = DummyOperator(task_id="task_1")
        task_2 = BashOperator(task_id="task_2", bash_command="echo 1")
        task_3 = DummyOperator(task_id="task_3")

        task_1 >> [task_2, task_3]

    with TaskGroup(
        "section_2", tooltip="Tasks for section_2", default_args={"owner": "overwrite"}
    ) as section_2:
        task_1 = DummyOperator(task_id="task_1")

    section_3 = TaskGroup("section_3", tooltip="Tasks for section_3", default_args={"owner": "bug"})

    end = DummyOperator(task_id="end", task_group=section_3)

    start >> section_1 >> section_2 >> section_3
```

### Anything else

_No response_

### 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
if ti.end_date:
                    dttm = wwwutils.epoch(ti.execution_date)
                    secs = (ti.end_date - ts).total_seconds()
                    x_points[task_id].append(dttm)
                    y_points[task_id].append(secs)
        
        
        y_unit = infer_time_unit([d for t in y_points.values() for d in t])
        
        chart.create_y_axis('yAxis', format='.02f', custom_format=False, label=f'Landing Time ({y_unit})')
        chart.axislist['yAxis']['axisLabelDistance'] = '-15'
        for task_id in x_points:
            chart.add_serie(
                name=task_id,
                x=x_points[task_id],
                y=scale_time_units(y_points[task_id], y_unit),
            )
        dates = sorted({ti.execution_date for ti in tis})
        max_date = max(ti.execution_date for ti in tis) if dates else None
        session.commit()
        form = DateTimeWithNumRunsForm(
            data={
                'base_date': max_date or timezone.utcnow(),
                'num_runs': num_runs,
            }
        )
        chart.buildcontent()
        return self.render_template(
            'airflow/chart.html',
            dag=dag,