fix(module:code-editor): resolve memory leak

[arturovt]

PR Checklist

• 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

[x] Bugfix

What is the current behavior?

I've noticed the NzCodeEditorService cannot be GC'd since it subscribes configUpdated$ which is a subject and keeps subscribers in its observers property until it's teardowned. This creates a memory leak for server-side rendered applications since the NzCodeEditorService is created and destroyed there per each HTTP request.

What is the new behavior?

The NzCodeEditorService is GC'd successfully.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #6846 (b13ff2c) into master (29d44af) will decrease coverage by 0.01%.
The diff coverage is 20.00%.

@@            Coverage Diff             @@
##           master    #6846      +/-   ##
==========================================
- Coverage   89.55%   89.53%   -0.02%     
==========================================
  Files         489      489              
  Lines       15796    15799       +3     
  Branches     2427     2427              
==========================================
  Hits        14146    14146              
- Misses       1008     1011       +3     
  Partials      642      642              

Impacted Files	Coverage Δ
components/code-editor/code-editor.service.ts	18.30% <20.00%> (-0.81%)	⬇️
components/tabs/tab-nav-bar.component.ts	83.03% <0.00%> (ø)

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[hsuanxyz]

LGTM