Kernel+Userland: Remove shared buffers (shbufs)

All users of this mechanism have been switched to anonymous files and
passing file descriptors with sendfd()/recvfd().

Shbufs got us where we are today, but it's time we say good-bye to them
and welcome a much more idiomatic replacement. :^)

Kernel/Process.cpp

@@ -45,10 +45,10 @@
 #include <Kernel/PerformanceEventBuffer.h>
 #include <Kernel/Process.h>
 #include <Kernel/RTC.h>
-#include <Kernel/SharedBuffer.h>
 #include <Kernel/StdLib.h>
 #include <Kernel/TTY/TTY.h>
 #include <Kernel/Thread.h>
+#include <Kernel/VM/AnonymousVMObject.h>
 #include <Kernel/VM/PageDirectory.h>
 #include <Kernel/VM/PrivateInodeVMObject.h>
 #include <Kernel/VM/ProcessPagingScope.h>
@@ -644,7 +644,6 @@ void Process::finalize()
 
     m_dead = true;
 
-    disown_all_shared_buffers();
     {
         // FIXME: PID/TID BUG
         if (auto parent_thread = Thread::from_tid(m_ppid.value())) {