Decouple openzeppelin testing versioning

[ericnordelo]

This PR decouples the version of openzeppelin_testing from the library version used for the rest of the packages.

It removes the documentation entry from the doc-site, since this one is pegged to the library version, and includes a local docs folder in markdown format generated by using scarb doc

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.51%. Comparing base (d6c2469) to head (6f87a86).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1366   +/-   ##
=======================================
  Coverage   92.51%   92.51%           
=======================================
  Files          81       81           
  Lines        3526     3526           
=======================================
  Hits         3262     3262           
  Misses        264      264           

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[immrsd]

Reviewed the prepare-release workflows thoroughly and ran through the .md files. Good job, LGTM!