fix(module:date-picker): get input width before panel open

[wenqi73]

Fixes #5320

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?

[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?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[zorro-bot]

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[codecov]

Codecov Report

Merging #5357 into master will increase coverage by 0.00%.
The diff coverage is 50.00%.

@@           Coverage Diff           @@
##           master    #5357   +/-   ##
=======================================
  Coverage   91.35%   91.36%           
=======================================
  Files         551      551           
  Lines       13909    13909           
  Branches     2099     2099           
=======================================
+ Hits        12707    12708    +1     
  Misses        712      712           
+ Partials      490      489    -1     

Impacted Files	Coverage Δ
components/date-picker/picker.component.ts	95.65% <50.00%> (+0.62%)	⬆️

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