Fix deprecations and errors

[AndrewKahr]

Changes

• Replace setoutput with the new environment output method
• Update node12 to node16
• Add the test package to unity modules to fix build errors on 2022.2 (Only applied to Unity 2020+ as that is when the package came into support)
• Lock UnityHub version to a defined value rather than the latest version at the time of build (matches Linux behavior)
• Add --no-sandbox flag to UnityHub in preparation for the latest v3 release that should allow us to build 2022.2 properly

Checklist

• [x] Read the contribution guide and accept the code of conduct
• [x] Readme (updated or not needed)

[github-actions[bot]]

[AndrewKahr]

I can't tell why but I've added --no-sandbox to the editor dockerfile when installing editors via the hub but I don't see the pr CI running with that flag. Does it not test PR code?