Test classes in parallel, 1 class per CPU core
Revert "Test classes in parallel, 1 class per CPU core"

This reverts commit 468002e3e66395562d48d5dd1a954bd10ff9c6f9.
Revert "Allow separate test classes to execute in parallel"

This reverts commit 02888396e6d47f94050963a5a19980d3ba3c578f.
Revert "Reduce test time on multi-core - fork 1 test process per core"

This reverts commit 74e40f3f61de08d207baf2f51300d9e69f5c3ed1.