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/ProcessProcFSTraits.cpp

@@ -36,7 +36,7 @@ InodeIndex Process::ProcessProcFSTraits::component_index() const
     return SegmentedProcFSIndex::build_segmented_index_for_pid_directory(process->pid());
 }
 
-ErrorOr<NonnullRefPtr<Inode>> Process::ProcessProcFSTraits::to_inode(ProcFS const& procfs_instance) const
+ErrorOr<NonnullLockRefPtr<Inode>> Process::ProcessProcFSTraits::to_inode(ProcFS const& procfs_instance) const
 {
     auto process = m_process.strong_ref();
     if (!process)