Kernel: Make self-contained locking smart pointers their own classes

Until now, our kernel has reimplemented a number of AK classes to
provide automatic internal locking:

- RefPtr
- NonnullRefPtr
- WeakPtr
- Weakable

This patch renames the Kernel classes so that they can coexist with
the original AK classes:

- RefPtr => LockRefPtr
- NonnullRefPtr => NonnullLockRefPtr
- WeakPtr => LockWeakPtr
- Weakable => LockWeakable

The goal here is to eventually get rid of the Lock* classes in favor of
using external locking.

Kernel/FileSystem/Mount.h

@@ -6,9 +6,9 @@
 
 #pragma once
 
-#include <AK/NonnullRefPtr.h>
 #include <Kernel/FileSystem/Custody.h>
 #include <Kernel/Forward.h>
+#include <Kernel/Library/NonnullLockRefPtr.h>
 
 namespace Kernel {
 
@@ -32,9 +32,9 @@ public:
     void set_flags(int flags) { m_flags = flags; }
 
 private:
-    NonnullRefPtr<Inode> m_guest;
-    NonnullRefPtr<FileSystem> m_guest_fs;
-    RefPtr<Custody> m_host_custody;
+    NonnullLockRefPtr<Inode> m_guest;
+    NonnullLockRefPtr<FileSystem> m_guest_fs;
+    LockRefPtr<Custody> m_host_custody;
     int m_flags;
 };