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/InodeWatcher.h

@@ -40,7 +40,7 @@ private:
 
 class InodeWatcher final : public File {
 public:
-    static ErrorOr<NonnullRefPtr<InodeWatcher>> try_create();
+    static ErrorOr<NonnullLockRefPtr<InodeWatcher>> try_create();
     virtual ~InodeWatcher() override;
 
     virtual bool can_read(OpenFileDescription const&, u64) const override;