refactor(module:transfer): refactor

[Ricbet]

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)
[x] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[x] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #4634

What is the new behavior?

Add NzSelectedKeys property. Sync antd

Does this PR introduce a breaking change?

[] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #4985 into master will decrease coverage by 0.06%.
The diff coverage is 27.27%.

@@            Coverage Diff             @@
##           master    #4985      +/-   ##
==========================================
- Coverage   91.49%   91.43%   -0.07%     
==========================================
  Files         548      548              
  Lines       13771    13782      +11     
  Branches     2044     2046       +2     
==========================================
+ Hits        12600    12601       +1     
- Misses        709      717       +8     
- Partials      462      464       +2     

Impacted Files	Coverage Δ
components/transfer/transfer-list.component.ts	96.29% <ø> (ø)
components/transfer/transfer-search.component.ts	100.00% <ø> (ø)
components/transfer/transfer.module.ts	100.00% <ø> (ø)
components/transfer/transfer.component.ts	92.00% <27.27%> (ø)
components/core/util/text-measure.ts	89.56% <0.00%> (-1.74%)	⬇️

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