refactor: use <nz-icon> to instead of [nz-icon]

[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

What is the new behavior?

将所有 [nz-icon] 替换为推荐的 <nz-icon> 写法。

如果用户在 CSS 中使用了 [nz-icon] 属性选择器去选择 zorro 组件内部的 icon，则需要更新为使用元素选择器。

组件内部的 DOM 结构通常不是 public 的，这属于 breaking changes 吗？

如果属于 breaking changes，那么应该也可以进入 beta 版本中。

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 91.93%. Comparing base (2e0c78d) to head (46a01ab).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8927      +/-   ##
==========================================
+ Coverage   91.91%   91.93%   +0.01%     
==========================================
  Files         554      554              
  Lines       19682    19680       -2     
  Branches     2936     2936              
==========================================
+ Hits        18091    18092       +1     
+ Misses       1265     1263       -2     
+ Partials      326      325       -1     

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[Laffery]

我认为属于 breaking changes，事实上 19.0.0-beta.0 中我们已经在一些组件中将 [nz-icon] 改成了 <nz-icon>，已经可能会导致用户原来 css 中的选择器失效。
所以我觉得我们不妨在这个 major 版本一次性做完，并且在 release note 中声明后续组件内部都会采用 <nz-icon> 写法，如果需要选择内部元素请更新为新选择器。用户组件自行根据偏好管理

[Laffery]

LGTM