Kernel/Memory: Fix overcommit when cloning anonymous mmap objects

AnonymousVMObject::try_clone() computed how many shared cow pages to
commit by counting all VMObject pages that were not shared_zero_pages.

This means that lazy_committed_pages were also being included in the
count. This is a problem because the page fault handling code for
lazy_committed_pages does not allocate from
m_shared_committed_cow_pages. So more pages than necessary were being
committed.

This fixes this overcommitting problem by skipping lazy_committed_pages
when counting how many pages to commit.

Kernel/Memory/AnonymousVMObject.cpp

@@ -34,7 +34,7 @@ ErrorOr<NonnullLockRefPtr<VMObject>> AnonymousVMObject::try_clone()
     // non-volatile memory available.
     size_t new_cow_pages_needed = 0;
     for (auto const& page : m_physical_pages) {
-        if (!page->is_shared_zero_page())
+        if (!page->is_shared_zero_page() && !page->is_lazy_committed_page())
             ++new_cow_pages_needed;
     }