Kernel+LibC: Move errno definitions to Kernel/API/POSIX

This fixes at least half of our LibC includes in the kernel. The source
of truth for errno codes and their description strings now lives in
Kernel/API/POSIX/errno.h as an enumeration, which LibC includes.

Kernel/FileSystem/OpenFileDescription.cpp

@@ -6,6 +6,7 @@
  */
 
 #include <AK/MemoryStream.h>
+#include <Kernel/API/POSIX/errno.h>
 #include <Kernel/Debug.h>
 #include <Kernel/Devices/BlockDevice.h>
 #include <Kernel/FileSystem/Custody.h>
@@ -20,7 +21,6 @@
 #include <Kernel/TTY/MasterPTY.h>
 #include <Kernel/TTY/TTY.h>
 #include <Kernel/UnixTypes.h>
-#include <LibC/errno_numbers.h>
 
 namespace Kernel {