AK: Make Vector::unstable_remove() return the removed value

...and rename it to unstable_take(), to align with other take...() methods.

AK/Vector.h

@@ -310,11 +310,11 @@ public:
         return value;
     }
 
-    void unstable_remove(size_t index)
+    T unstable_take(size_t index)
     {
         ASSERT(index < m_size);
         swap(at(index), at(m_size - 1));
-        take_last();
+        return take_last();
     }
 
     void remove(size_t index)

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -119,7 +119,7 @@ KResult VFS::unmount(Inode& guest_inode)
                 return result;
             }
             dbg() << "VFS: found fs " << mount.guest_fs().fsid() << " at mount index " << i << "! Unmounting...";
-            m_mounts.unstable_remove(i);
+            m_mounts.unstable_take(i);
             return KSuccess;
         }
     }

Kernel/Process.cpp

@@ -237,7 +237,7 @@ bool Process::deallocate_region(Region& region)
         m_region_lookup_cache.region = nullptr;
     for (size_t i = 0; i < m_regions.size(); ++i) {
         if (&m_regions[i] == &region) {
-            m_regions.unstable_remove(i);
+            m_regions.unstable_take(i);
             return true;
         }
     }

Kernel/SharedBuffer.cpp

@@ -156,7 +156,7 @@ void SharedBuffer::disown(pid_t pid)
             dbg() << "Disowning shared buffer " << m_shbuf_id << " of size " << size() << " by PID " << pid;
 #endif
             m_total_refs -= ref.count;
-            m_refs.unstable_remove(i);
+            m_refs.unstable_take(i);
 #ifdef SHARED_BUFFER_DEBUG
             dbg() << "Disowned shared buffer " << m_shbuf_id << " of size " << size() << " by PID " << pid;
 #endif