Everywhere: Move global Kernel pattern code to Kernel/Library directory

This has KString, KBuffer, DoubleBuffer, KBufferBuilder, IOWindow,
UserOrKernelBuffer and ScopedCritical classes being moved to the
Kernel/Library subdirectory.

Also, move the panic and assertions handling code to that directory.

Kernel/Net/NetworkingManagement.cpp

@@ -7,7 +7,7 @@
 #include <AK/Singleton.h>
 #include <Kernel/Bus/PCI/API.h>
 #include <Kernel/CommandLine.h>
-#include <Kernel/KString.h>
+#include <Kernel/Library/KString.h>
 #include <Kernel/Memory/AnonymousVMObject.h>
 #include <Kernel/Multiboot.h>
 #include <Kernel/Net/Intel/E1000ENetworkAdapter.h>