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/IPv4SocketTuple.h

@@ -7,9 +7,9 @@
 #pragma once
 
 #include <AK/HashMap.h>
-#include <Kernel/DoubleBuffer.h>
-#include <Kernel/KBuffer.h>
-#include <Kernel/KString.h>
+#include <Kernel/Library/DoubleBuffer.h>
+#include <Kernel/Library/KBuffer.h>
+#include <Kernel/Library/KString.h>
 #include <Kernel/Locking/Mutex.h>
 #include <Kernel/Net/IPv4.h>
 #include <Kernel/Net/Socket.h>