feat(module:icon): support import icon in submodules

[wzhudev]

close #4668

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

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #4673 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #4673      +/-   ##
=========================================
- Coverage   93.25%   93.2%   -0.05%     
=========================================
  Files         505     517      +12     
  Lines       12734   12824      +90     
  Branches     1957    2020      +63     
=========================================
+ Hits        11875   11953      +78     
- Misses        447     455       +8     
- Partials      412     416       +4

Impacted Files	Coverage Δ
components/icon/nz-icon.directive.ts	96.61% <100%> (+0.11%)	⬆️
components/icon/nz-icon.service.ts	98.43% <100%> (+0.28%)	⬆️
components/icon/nz-icon.module.ts	100% <100%> (ø)	⬆️
components/core/testing/componet-bed.ts	81.81% <0%> (-9.1%)	⬇️
components/core/testing/event-objects.ts	89.28% <0%> (-4.27%)	⬇️
...ore/transition-patch/transition-patch.directive.ts	89.65% <0%> (-3.68%)	⬇️
components/tabs/nz-tabset.component.ts	93.42% <0%> (-1.32%)	⬇️
components/core/util/convert.ts	84.61% <0%> (-1.1%)	⬇️
components/typography/nz-typography.component.ts	98.23% <0%> (-0.89%)	⬇️
components/date-picker/lib/util.ts	97.05% <0%> (-0.24%)	⬇️
... and 167 more

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[wzhudev]

得，codecov 又歇逼了

[wzhudev]

I will move this feature into #4711. Closing now.