fix(module:date-picker): ng-untouched when loose focus

[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

This PR introduce a bug fix.

[x] 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?

Before this PR, when the user loose the focus without selected a value of date-picker input, datapicker control stay untouched

Issue Number: #7879

What is the new behavior?

When the user loose the focus without selected a date, datePicker control become touched

Does this PR introduce a breaking change?

[ ] Yes
[X] No

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #7922 (0a0fde5) into master (59143d2) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

❗ Current head 0a0fde5 differs from pull request most recent head 68f4773. Consider uploading reports for the commit 68f4773 to get more accurate results

@@            Coverage Diff             @@
##           master    #7922      +/-   ##
==========================================
- Coverage   91.78%   91.74%   -0.04%     
==========================================
  Files         509      509              
  Lines       17444    17445       +1     
  Branches     2683     2683              
==========================================
- Hits        16011    16005       -6     
- Misses       1134     1142       +8     
+ Partials      299      298       -1     

Impacted Files	Coverage Δ
components/date-picker/date-picker.component.ts	94.64% <100.00%> (+0.01%)	⬆️

... and 5 files with indirect coverage changes

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