fix(module:drawer): content is attached before the drawer is opened

[hsuanxyz]

fix #6381, close #6534

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: #6381

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 #6581 (84694e3) into master (21ded3f) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 84694e3 differs from pull request most recent head bfe26a3. Consider uploading reports for the commit bfe26a3 to get more accurate results

@@           Coverage Diff           @@
##           master    #6581   +/-   ##
=======================================
  Coverage   89.92%   89.92%           
=======================================
  Files         481      481           
  Lines       15375    15381    +6     
  Branches     2344     2344           
=======================================
+ Hits        13826    13832    +6     
  Misses        929      929           
  Partials      620      620           

Impacted Files	Coverage Δ
components/drawer/drawer.component.ts	97.08% <100.00%> (-0.92%)	⬇️
components/time-picker/time-holder.ts	95.78% <0.00%> (+1.05%)	⬆️
components/drawer/drawer-content.directive.ts	100.00% <0.00%> (+50.00%)	⬆️

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