fix(scroll dispatcher): emit scroll events from cdkScrollable directive

[yggg]

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• I read and followed the CONTRIBUTING.md guide.
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Short description of what this resolves:

[codecov]

Codecov Report

Merging #2714 (1a15996) into master (db9e556) will increase coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2714      +/-   ##
==========================================
+ Coverage   77.82%   77.91%   +0.09%     
==========================================
  Files         262      262              
  Lines        8229     8229              
  Branches      896      896              
==========================================
+ Hits         6404     6412       +8     
+ Misses       1550     1540      -10     
- Partials      275      277       +2     

Impacted Files	Coverage Δ
...omponents/cdk/adapter/scroll-dispatcher-adapter.ts	100.00% <100.00%> (ø)
...mework/theme/components/sidebar/sidebar.service.ts	90.62% <100.00%> (+18.75%)	⬆️
...work/theme/components/sidebar/sidebar.component.ts	77.33% <0.00%> (+1.33%)	⬆️