fix(Sidebar): fix issue with Portals in React 17

[layershifter]

Fixes #4110.

A fix was done in microsoft/fluentui#16514, the issue is related to a bug in React (facebook/react#20074). An integration test was added to ensure that the issue was actually fixed.

[github-actions]

size-limit report

Path	Size
bundle-size/dist/Button.size.js	58.58 KB (0%)
bundle-size/dist/Icon.size.js	25.06 KB (0%)
bundle-size/dist/Image.size.js	53.76 KB (0%)
bundle-size/dist/Modal.size.js	68.66 KB (0%)
bundle-size/dist/Portal.size.js	40.46 KB (0%)

[codecov-io]

Codecov Report

Merging #4144 (33d95c7) into master (d2be2e0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4144   +/-   ##
=======================================
  Coverage   99.75%   99.75%           
=======================================
  Files         180      180           
  Lines        3241     3241           
=======================================
  Hits         3233     3233           
  Misses          8        8           

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