Add standalone testmode support (#219)

* Add standalone support.

* Add standalone tests.

* UnityStandaloneScripts volume on windows

* Update test framework in test project.

* Revert IL2CPP setting in test project.
Add test for IL2CPP.

* Update dist/test-standalone-scripts/Assets/Player/UnityTestRunnerAction/TestRunCallback.cs

Co-authored-by: Webber Takken <webber.nl@gmail.com>

* Use 2019.2.21f1

* Unity is being dumb, use 2019.4.40f1 for all workflows.

* Disable PlayerConnection on build.
Print player log.

* Add comment about code coverage support in standalone.

* Update node-version in test

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Co-authored-by: Webber Takken <webber.nl@gmail.com>

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