Revert React Portals for most uses

[ellatrix]

See #3082.
This reverts commit 1fbb24f.

[codecov]

Codecov Report

Merging #3083 into master will increase coverage by 1.42%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #3083      +/-   ##
==========================================
+ Coverage   32.32%   33.75%   +1.42%     
==========================================
  Files         216      217       +1     
  Lines        6134     6609     +475     
  Branches     1079     1191     +112     
==========================================
+ Hits         1983     2231     +248     
- Misses       3502     3682     +180     
- Partials      649      696      +47

Impacted Files	Coverage Δ
blocks/editable/index.js	10.5% <ø> (ø)	⬆️
blocks/inspector-controls/index.js	88.88% <ø> (ø)	⬆️
blocks/block-controls/index.js	0% <ø> (ø)	⬆️
editor/sidebar/block-inspector/index.js	0% <0%> (ø)	⬆️
editor/provider/index.js	0% <0%> (ø)	⬆️
editor/block-toolbar/index.js	0% <0%> (ø)	⬆️
editor/block-settings-menu/content.js	11.53% <0%> (-15.74%)	⬇️
blocks/library/html/index.js	19.04% <0%> (-4.03%)	⬇️
blocks/library/latest-posts/index.js	7.22% <0%> (-2.78%)	⬇️
editor/modes/visual-editor/inserter.js	91.66% <0%> (-1.67%)	⬇️
... and 17 more

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[youknowriad]

Sorry for not catching the issues on the first review.