fix(module:date-picker): cell title should reflect nzFormat

[RubenVermeulen]

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: #8743

What is the new behavior?

The cell title of the date picker reflects nzFormat instead of relying on the locale setting.

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

All modified and coverable lines are covered by tests ✅

Project coverage is 91.90%. Comparing base (b382b58) to head (f8ab118).
Report is 139 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8744      +/-   ##
==========================================
- Coverage   93.15%   91.90%   -1.25%     
==========================================
  Files         538      555      +17     
  Lines       18456    19708    +1252     
  Branches     2816     2943     +127     
==========================================
+ Hits        17192    18113     +921     
- Misses       1226     1268      +42     
- Partials       38      327     +289     

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[Laffery]

LGTM