fix(module:select): activated value resetting during load on scroll

[dev-anton-ko]

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?

• Load on Scroll - Activated Value resets to zero position after the adding of new page of data
• Multiple Selection - After selecting an item Activated Value resets to the first selected element instead of staying the same. And one have to navigate through all the list again to continue selection. It's significant for selecting by keyboard.

Issue Number: N/A

What is the new behavior?

• Load on Scroll - Activated Value shifts to the next item of the list
• Multiple Selection - After selecting an item Activated Value stays the same

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #7725 (5d75470) into master (f6a8044) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #7725   +/-   ##
=======================================
  Coverage   92.03%   92.03%           
=======================================
  Files         502      502           
  Lines       16763    16764    +1     
  Branches     2638     2638           
=======================================
+ Hits        15427    15428    +1     
  Misses       1069     1069           
  Partials      267      267           

Impacted Files	Coverage Δ
components/select/select.component.ts	91.31% <100.00%> (+0.02%)	⬆️

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[simplejason]

LGTM