select下拉选中的元素内容太长时没有显示省略号，都占据了右边的icon图标位置

[DavidYangLin]

Reproduction link

https://ng-zorro-antd-start-p2yqhh.stackblitz.io

Steps to reproduce

选择长达下拉元素即可看到

What is expected?

希望下拉选中的元素内容超过select框长度时，能够显示省略号，不要占据右边icon的位置

What is actually happening?

元素没有显示省略号，并且占用了icon的位置

Environment	Info
ng-zorro-antd	8.0.1
Browser	chrome

[zorro-bot]

Translation of this issue:

When the content of the select drop-down element is too long, no ellipsis is displayed, and the icon icon position on the right side is occupied.

Reproduction link

https://ng-zorro-antd-start-p2yqhh.stackblitz.io

Steps to reproduce

Select the long drop down element to see

What is expected?

If you want the content of the selected element to exceed the length of the select box, you can display the ellipsis and do not occupy the position of the icon on the right.

What is actually happening?

The element does not display an ellipsis and takes up the position of the icon

Environment	Info
ng-zorro-antd	8.0.1
Browser	chrome