As means to pave the way for getting rid of global state within core, This eliminates kernel global state by removing all globals. Instead this introduces a KernelCore class which acts as a kernel instance. This instance lives in the System class, which keeps its lifetime contained to the lifetime of the System class. This also forces the kernel types to actually interact with the main kernel instance itself instead of having transient kernel state placed all over several translation units, keeping everything together. It also has a nice consequence of making dependencies much more explicit. This also makes our initialization a tad bit more correct. Previously we were creating a kernel process before the actual kernel was initialized, which doesn't really make much sense. The KernelCore class itself follows the PImpl idiom, which allows keeping all the implementation details sealed away from everything else, which forces the use of the exposed API and allows us to avoid any unnecessary inclusions within the main kernel header.