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/Net/NE2000/NetworkAdapter.h

@@ -20,7 +20,7 @@ class NE2000NetworkAdapter final : public NetworkAdapter
     , public PCI::Device
     , public IRQHandler {
 public:
-    static RefPtr<NE2000NetworkAdapter> try_to_initialize(PCI::DeviceIdentifier const&);
+    static LockRefPtr<NE2000NetworkAdapter> try_to_initialize(PCI::DeviceIdentifier const&);
 
     virtual ~NE2000NetworkAdapter() override;