Github Action split in jobs and matrix steps

[opatry]

Description

• Refactor build job as parallel job with nested matrix when relevant
  • Fix Gradle failure comment publish
  • Improve stale credits PR comment (and remove deprecated ::set-output)
  • Extract common JDK+Gradle setup in a reusable action
  • When Android & Desktop are doing almost the same, use a matrix strategy
  • Execute builds on Linux (only stale credits are kept on macOS because generated locally bu developer on macOS and need "no-diff" when generated on CI… still a bit fragile in the process)
• Align Play Store publish job with build job refinements

Checklist

• I have read the CONTRIBUTING guide
• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing