feat(module:float-button): support nzPlacement

[WwwHhhYran]

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 new behavior?

you can set nzPlacement for nz-float-button-group to customize the pop placement of its menu buttons

Does this PR introduce a breaking change?

• Yes
• No

Other information

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Attention: Patch coverage is 93.47826% with 3 lines in your changes missing coverage. Please review.

Project coverage is 92.14%. Comparing base (ff1fa28) to head (49232aa).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...nents/float-button/float-button-group.component.ts	93.47%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9267      +/-   ##
==========================================
+ Coverage   92.06%   92.14%   +0.07%     
==========================================
  Files         561      561              
  Lines       19609    19608       -1     
  Branches     3102     3102              
==========================================
+ Hits        18054    18068      +14     
+ Misses       1215     1202      -13     
+ Partials      340      338       -2     

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[Nicoss54]

LGTM

[Laffery]

LGTM