feat(module:breadcrumb): support dropdown

[wzhudev]

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
[x] 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
[ ] No

Other information

[netlify]

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Built with commit a0a454c

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[codecov]

Codecov Report

Merging #3636 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3636      +/-   ##
==========================================
+ Coverage   95.46%   95.47%   +<.01%     
==========================================
  Files         685      686       +1     
  Lines       14080    14088       +8     
  Branches     1874     1875       +1     
==========================================
+ Hits        13442    13450       +8     
  Misses        226      226              
  Partials      412      412

Impacted Files	Coverage Δ
...ponents/breadcrumb/nz-breadcrumb-item.component.ts	100% <100%> (ø)	⬆️
components/breadcrumb/demo/dropdown.ts	100% <100%> (ø)
components/breadcrumb/nz-breadcrumb.module.ts	100% <100%> (ø)	⬆️
components/form/nz-form-control.component.ts	93.61% <0%> (+0.06%)	⬆️

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[vthinkxie]

LGTM