Kernel: Release page directory and MM locks sooner in space finalization

We don't need to hold these locks when tearing down the region tree.
Release them as soon as unmapping is finished.

Kernel/Memory/AddressSpace.cpp

@@ -321,10 +321,12 @@ void AddressSpace::remove_all_regions(Badge<Process>)
 {
     VERIFY(Thread::current() == g_finalizer);
     SpinlockLocker locker(m_lock);
-    SpinlockLocker pd_locker(m_page_directory->get_lock());
-    SpinlockLocker mm_locker(s_mm_lock);
-    for (auto& region : m_regions)
-        (*region).unmap_with_locks_held(Region::ShouldDeallocateVirtualRange::No, ShouldFlushTLB::No, pd_locker, mm_locker);
+    {
+        SpinlockLocker pd_locker(m_page_directory->get_lock());
+        SpinlockLocker mm_locker(s_mm_lock);
+        for (auto& region : m_regions)
+            (*region).unmap_with_locks_held(Region::ShouldDeallocateVirtualRange::No, ShouldFlushTLB::No, pd_locker, mm_locker);
+    }
     m_regions.clear();
 }