[$] Toward the unification of kselftests and KUnit

The kernel project, for many years, lacked a formal testing setup; it wasoften joked that testing was the project's main reason for keeping usersaround. While many types of kernel testing can only be done in thepresence of specific hardware, there are other parts of the kernelthat could be more widely tested. Over time, though, the kernel has gainedtwo separate testing frameworks and a growing body of automated tests to gowith them. These two frameworks - kselftests and KUnit - take differentapproaches to the testing problem; now thispatch series from Thomas Weischuh aims to bring them together.