feat(module:alert): support nzAction for customizing actions

[yangjunhan]

close #7245

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: #7245

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #7246 (41a37a2) into master (662648c) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #7246      +/-   ##
==========================================
- Coverage   91.72%   91.68%   -0.04%     
==========================================
  Files         486      486              
  Lines       15918    15919       +1     
  Branches     2588     2588              
==========================================
- Hits        14601    14596       -5     
- Misses       1004     1011       +7     
+ Partials      313      312       -1     

Impacted Files	Coverage Δ
components/alert/alert.component.ts	95.23% <100.00%> (+0.07%)	⬆️
components/table/src/table/tr-measure.component.ts	86.36% <0.00%> (-13.64%)	⬇️
components/table/src/table/tbody.component.ts	88.88% <0.00%> (-11.12%)	⬇️
...ts/table/src/table/table-inner-scroll.component.ts	79.41% <0.00%> (-4.42%)	⬇️
components/core/util/text-measure.ts	92.98% <0.00%> (+0.87%)	⬆️
components/table/src/table-style.service.ts	96.55% <0.00%> (+1.72%)	⬆️

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[simplejason]

LGTM