fix(module:popconfirm): correctly render icon and title

[HyperLife1119]

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

• 当 nzTitle 传入类型为 TemplateRef 时，icon 不会被渲染，这是错误的，title 不应该影响 icon 的渲染；如果不想渲染 icon，应当将 nzIcon 设置为 null。
• 自定义 icon 时候，没有将 icon 渲染在 ant-popover-message-icon 下（缺少右边距）。

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.12%. Comparing base (77e0b62) to head (14d87c1).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9322   +/-   ##
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  Coverage   92.12%   92.12%           
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  Files         561      561           
  Lines       19631    19631           
  Branches     3107     3107           
=======================================
  Hits        18086    18086           
  Misses       1206     1206           
  Partials      339      339           

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[Laffery]

LGTM