Kernel: Require lock rank for Spinlock construction

All users which relied on the default constructor use a None lock rank
for now. This will make it easier to in the future remove LockRank and
actually annotate the ranks by searching for None.

Kernel/Memory/AnonymousVMObject.h

@@ -78,7 +78,7 @@ private:
         void uncommit_one();
 
     private:
-        Spinlock m_lock;
+        Spinlock m_lock { LockRank::None };
         CommittedPhysicalPageSet m_committed_pages;
     };