feat(module:select): add nzOnClear callback

[Nicoss54]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Application (the showcase website) / infrastructure changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[zorro-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 23.70%. Comparing base (e48d672) to head (4a1ffa1).
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #9188       +/-   ##
===========================================
- Coverage   92.08%   23.70%   -68.39%     
===========================================
  Files         561      561               
  Lines       19883    19885        +2     
  Branches     3005     3005               
===========================================
- Hits        18309     4713    -13596     
- Misses       1234    15135    +13901     
+ Partials      340       37      -303     

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[HyperLife1119]

LGTM

[Laffery]

I think the description of nzOnClear should be changed :)

[Nicoss54]

@Laffery documentation is changed

[Laffery]

LGTM