Kernel+LibC: Move name length constants to Kernel/API from limits.h

Reduce inclusion of limits.h as much as possible at the same time.

This does mean that kmalloc.h is now including Kernel/API/POSIX/limits.h
instead of LibC/limits.h, but the scope could be limited a lot more.
Basically every file in the kernel includes kmalloc.h, and needs the
limits.h include for PAGE_SIZE.

Kernel/API/InodeWatcherEvent.h

@@ -10,7 +10,7 @@
 #include <AK/Types.h>
 
 #ifdef KERNEL
-#    include <LibC/limits.h>
+#    include <Kernel/API/POSIX/sys/limits.h>
 #else
 #    include <limits.h>
 #endif