Add a simplified EachBlock helper

[Swatinem]

This introduces a EachBlock helper instead of generating specific code for each blocks, as suggested here: #3504 (comment)

So far this is only used in certain conditions, as the full
feature set is not implemented yet.
Also, thinking about this a bit more, maybe instead of a full blown class, it would be a better idea to use some functional helpers? Especially when getting transitions to work would mean that each blocks would essentially pull in all the transition related runtime… I don’t think that’s too desirable.

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Tests

• Run the tests tests with npm test or yarn test)

[codecov-io]

Codecov Report

Merging #3540 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3540   +/-   ##
=======================================
  Coverage   50.25%   50.25%           
=======================================
  Files           1        1           
  Lines         197      197           
=======================================
  Hits           99       99           
  Misses         98       98

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[Swatinem]

superceded by #3547