fix(module:tree-view): fix innerTrackBy function #7118

[plakyda-codefresh]

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?

[x] 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?

1. default innerTrackBy function value being assigned on each OnChanges call
2. during scroll further and back of VirtualTree, nodes is broken

• Reproduce - Codesandbox

Issue Number: #7118

What is the new behavior?

1. innerTrackBy function value being assigned only in case when @Input trackBy changing
2. VirtualTree scroll recreates nodes as it should be

• Fixed VirtualTree - CodeSandbox

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #7150 (d9329e6) into master (c177558) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #7150   +/-   ##
=======================================
  Coverage   91.67%   91.67%           
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  Files         486      486           
  Lines       15868    15868           
  Branches     2587     2587           
=======================================
  Hits        14547    14547           
  Misses       1007     1007           
  Partials      314      314           

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[hsuanxyz]

LGTM

[plakyda-codefresh]

@hsuanxyz thanks 🙏
any plans to release?
it's broken in documentation