Blocks: Translate embed title prior to passing to settings factory

[aduth]

This pull request seeks to resolve invalid usage of i18n functions where string extraction by static analysis would be unable to retrieve the referenced string argument. There was one instance of this in the embed block.

Further, the behavior of the embed block was such that it would attempt to translate titles for services such as YouTube, etc. Since these are brands, they are not intended to be translatable.

Finally, in order to prevent against future issues, I've introduced new lint rules for restricted syntax which will capture these errors during CI.

Testing instructions:

Verify that generating gettext strings includes the "Embed" string, and not any of the other embed services.

npm run test-client

Try locally to update the invocation of __, _n, _x, or _nx to include an argument which is not either a string or concatenated string (see #2655), and confirm that linting fails:

npm run lint

[codecov]

Codecov Report

Merging #2687 into master will increase coverage by 1.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2687      +/-   ##
==========================================
+ Coverage   33.15%   34.17%   +1.01%     
==========================================
  Files         182      185       +3     
  Lines        5540     5653     +113     
  Branches      963      994      +31     
==========================================
+ Hits         1837     1932      +95     
- Misses       3136     3153      +17     
- Partials      567      568       +1

Impacted Files	Coverage Δ
blocks/library/embed/index.js	45.55% <ø> (ø)	⬆️
editor/modes/visual-editor/block.js	0% <0%> (ø)	⬆️
editor/modes/visual-editor/block-crash-boundary.js	0% <0%> (ø)	⬆️
utils/focus/test/utils/create-element.js	100% <0%> (ø)
utils/focus/focusable.js	93.33% <0%> (ø)
utils/focus/tabbable.js	100% <0%> (ø)
blocks/api/validation.js	95.23% <0%> (+0.07%)	⬆️
blocks/api/serializer.js	98% <0%> (+0.08%)	⬆️
blocks/api/parser.js	98.3% <0%> (+0.15%)	⬆️
editor/inserter/menu.js	49.61% <0%> (+1.2%)	⬆️
... and 1 more

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