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/Storage/StorageManagement.cpp

@@ -230,7 +230,7 @@ UNMAP_AFTER_INIT void StorageManagement::determine_boot_device_with_partition_uu
     }
 }
 
-RefPtr<BlockDevice> StorageManagement::boot_block_device() const
+LockRefPtr<BlockDevice> StorageManagement::boot_block_device() const
 {
     return m_boot_block_device.strong_ref();
 }
@@ -254,7 +254,7 @@ u32 StorageManagement::generate_controller_id()
     return s_controller_id.fetch_add(1);
 }
 
-NonnullRefPtr<FileSystem> StorageManagement::root_filesystem() const
+NonnullLockRefPtr<FileSystem> StorageManagement::root_filesystem() const
 {
     auto boot_device_description = boot_block_device();
     if (!boot_device_description) {