feat(module:upload): add directory support

[cipchk]

includes:

• add directory support
• cancel upload when return a false value in nzBeforeUpload, Missing observable boolean checking [nzBeforeUpload] #2167, #changed diff
  , #test diff

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
[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:

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #2164 into master will decrease coverage by 0.02%.
The diff coverage is 91.3%.

@@            Coverage Diff             @@
##           master    #2164      +/-   ##
==========================================
- Coverage      96%   95.98%   -0.03%     
==========================================
  Files         479      479              
  Lines       11697    11712      +15     
  Branches     1564     1569       +5     
==========================================
+ Hits        11230    11242      +12     
- Misses        132      133       +1     
- Partials      335      337       +2

Impacted Files	Coverage Δ
components/upload/nz-upload.component.ts	99.37% <100%> (-0.01%)	⬇️
components/upload/nz-upload-btn.component.ts	98.07% <90%> (-1.93%)	⬇️

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