fix(module:time-picker): add readonly attribute

[wenqi73]

Closes #5678
Closes #5741

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: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #5679 into master will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5679      +/-   ##
==========================================
- Coverage   90.09%   90.03%   -0.07%     
==========================================
  Files         455      455              
  Lines       13798    13794       -4     
  Branches     2183     2182       -1     
==========================================
- Hits        12431    12419      -12     
- Misses        843      851       +8     
  Partials      524      524              

Impacted Files	Coverage Δ
components/time-picker/time-picker.component.ts	90.90% <ø> (-2.57%)	⬇️
components/core/util/text-measure.ts	89.56% <0.00%> (-1.74%)	⬇️
components/tabs/tab-nav-bar.component.ts	80.91% <0.00%> (-1.42%)	⬇️

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