Build file improvements

[rnc]

• Suppress cast warnings as we know the API returns those types
• Remove the redundant qualifier for org.gradle.util.GradleVersion but use gradle/fix-build.sh to patch it back in for Gradle < 7.1

Also improved the documentation to mention use of fix-build.sh.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.26%. Comparing base (83128b5) to head (f231e50).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #512   +/-   ##
=======================================
  Coverage   80.26%   80.26%           
=======================================
  Files          42       42           
  Lines        2600     2600           
  Branches      356      356           
=======================================
  Hits         2087     2087           
  Misses        383      383           
  Partials      130      130           

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