[Bug] The slider mode dataZoom should clip the background by the borderRadius property

### Version

6.0.0

### Link to Minimal Reproduction

N/A

### Steps to Reproduce

- Create a chart with a slider dataZoom.
- Specify a backgroundColor for the dataZoom
- Specify a borderRadius for the dataZoom

### Current Behavior

The background extends beyond the defined border radius.

### Expected Behavior

The background should not extend beyond the defined borderRadius.

### Environment

```markdown
- OS:
- Browser:
- Framework:
```

### Any additional comments?

Fixing this issue is trivial.

The current code:

```
SliderZoomView.prototype._renderBackground = function () {
var dataZoomModel = this.dataZoomModel;
var size = this._size;
var barGroup = this._displayables.sliderGroup;
var brushSelect = dataZoomModel.get('brushSelect');
barGroup.add(new Rect$2({
silent: true,
shape: {
x: 0,
y: 0,
width: size[0],
height: size[1]
},
style: {
fill: dataZoomModel.get('backgroundColor')
},
z2: -40
}));
```

Results in this:

Changing it to:

```
SliderZoomView.prototype._renderBackground = function () {
var dataZoomModel = this.dataZoomModel;
var size = this._size;
var barGroup = this._displayables.sliderGroup;
var brushSelect = dataZoomModel.get('brushSelect');
var borderRadius = dataZoomModel.get('borderRadius');
barGroup.add(new Rect$2({
silent: true,
shape: {
x: 0,
y: 0,
width: size[0],
height: size[1],
r: borderRadius
},
style: {
fill: dataZoomModel.get('backgroundColor')
},
z2: -40
}));
```

Results in a properly clipped rectange:

Start at SliderZoomView.prototype._renderBackground and inspect how the slider dataZoom background rectangle is created with Rect$2. Verify how borderRadius is obtained from the dataZoom model, then confirm that the background remains clipped to the rounded shape when backgroundColor and borderRadius are specified.

Written by the indexing model from the issue text.