feat(module:avatar): support custom icon

[OriginRing]

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)
• 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

All modified and coverable lines are covered by tests ✅

Project coverage is 91.99%. Comparing base (781ef0f) to head (6376ef2).
Report is 17 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9090      +/-   ##
==========================================
- Coverage   92.01%   91.99%   -0.02%     
==========================================
  Files         564      565       +1     
  Lines       20025    20062      +37     
  Branches     3106     3013      -93     
==========================================
+ Hits        18426    18457      +31     
- Misses       1261     1265       +4     
- Partials      338      340       +2     

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[HyperLife1119]

LGTM

[Laffery]

LGTM