feat(module:tooltip, etc): add arrow point at center

[wzhudev]

close #2858

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.

[wzhudev]

I am afraid that when used with nzNoAnimation it may shift the first time it appears. Need more investigation here. In the worst case we may need to implement a position strategy by ourselves.

It works. :)

[codecov]

Codecov Report

Merging #7010 (cfd5aad) into master (9700e89) will decrease coverage by 0.02%.
The diff coverage is 82.85%.

❗ Current head cfd5aad differs from pull request most recent head 752d43c. Consider uploading reports for the commit 752d43c to get more accurate results

@@            Coverage Diff             @@
##           master    #7010      +/-   ##
==========================================
- Coverage   89.51%   89.48%   -0.03%     
==========================================
  Files         488      488              
  Lines       15792    15822      +30     
  Branches     2435     2441       +6     
==========================================
+ Hits        14136    14159      +23     
- Misses       1016     1021       +5     
- Partials      640      642       +2     

Impacted Files	Coverage Δ
components/tooltip/base.ts	93.54% <60.00%> (+0.06%)	⬆️
components/core/overlay/nz-connected-overlay.ts	85.71% <84.61%> (-14.29%)	⬇️
components/popconfirm/popconfirm.ts	96.15% <100.00%> (+0.04%)	⬆️
components/popover/popover.ts	100.00% <100.00%> (ø)
components/tooltip/tooltip.ts	100.00% <100.00%> (ø)
components/time-picker/time-holder.ts	95.78% <0.00%> (-1.06%)	⬇️
components/tabs/tab-nav-bar.component.ts	81.56% <0.00%> (-0.71%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9700e89...752d43c. Read the comment docs.

[simplejason]

LGTM