DefaultTestExecuter hard-codes the use of ForkingTestClassProcessor. This pull request introduces a way to use alternative TestClassProcessor.

When running tests on Scala.js, forking is not an option, so Gradle Scala.js plugin needs to use a TestClassProcessor that does not fork.

Without an extension point, the only way to make this work is to fork DefaultTestExecuter class and track changes to its Gradle original in a different repository just to be able to override one method - which is sub-optimal ;)

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