feat(module:rate): add tooltip support

[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
[ ] Feature
[ ] Code style update (formatting, local variables)
[x] 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 #2794 into master will decrease coverage by 0.01%.
The diff coverage is 96.96%.

@@            Coverage Diff             @@
##           master    #2794      +/-   ##
==========================================
- Coverage   95.52%   95.51%   -0.02%     
==========================================
  Files         517      517              
  Lines       12258    12231      -27     
  Branches     1691     1689       -2     
==========================================
- Hits        11710    11682      -28     
- Misses        189      190       +1     
  Partials      359      359

Impacted Files	Coverage Δ
components/core/util/public-api.ts	100% <ø> (ø)	⬆️
components/icon/nz-icon.service.ts	98.27% <ø> (ø)	⬆️
components/rate/nz-rate.module.ts	100% <100%> (ø)	⬆️
components/rate/nz-rate-item.component.ts	91.66% <91.66%> (ø)
components/rate/nz-rate.component.ts	98.14% <98.07%> (-0.5%)	⬇️

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[netlify]

Deploy preview for ng-zorro-master ready!

Built with commit ae4f502

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[netlify]

Deploy preview for ng-zorro-master ready!

Built with commit 5adb7c7

https://deploy-preview-2794--ng-zorro-master.netlify.com

[vthinkxie]

LGTM