allocators: make crtdbg allocator reuse its own realloc In commit 6e0dfc6ff (Make stdalloc__reallocarray call stdalloc__realloc, 2019-02-16), we have changed the stdalloc allocator to reuse `stdalloc__realloc` to implement `stdalloc__reallocarray`. This commit is making the same change for the Windows-specific crtdbg allocator to avoid code duplication.