When the input element in nz-select is focused by pressing the "tab" key in a form, nz-select should also be auto-focus

[ousc]

Reproduction link

https://codesandbox.io/s/ng-zorro-antd-ivy-lcwx2?file=/src/app/app.component.ts

Steps to reproduce

click the input element and press "tab"

What is expected?

the select box is focused, and if the select box with property "showsearch", you can input directly

What is actually happening?

the nz-select-box is not focused

Environment	Info
ng-zorro-antd	9.1.2
Browser	chrome 83.0.4103.61（正式版本） （64 位）

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Maybe we can add a focus event to the input in the select to solve this problem.