Kernel: Move VM-related files into Kernel/VM/.

Also break MemoryManager.{cpp,h} into one file per class.

Kernel/VM/VMObject.h

@@ -0,0 +1,57 @@
+#pragma once
+
+#include <AK/Badge.h>
+#include <AK/Retainable.h>
+#include <AK/Weakable.h>
+#include <AK/RetainPtr.h>
+#include <AK/Vector.h>
+#include <AK/AKString.h>
+#include <Kernel/Lock.h>
+
+class Inode;
+class PhysicalPage;
+
+class VMObject : public Retainable<VMObject>, public Weakable<VMObject> {
+    friend class MemoryManager;
+public:
+    static Retained<VMObject> create_file_backed(RetainPtr<Inode>&&);
+    static Retained<VMObject> create_anonymous(size_t);
+    static Retained<VMObject> create_for_physical_range(PhysicalAddress, size_t);
+    Retained<VMObject> clone();
+
+    ~VMObject();
+    bool is_anonymous() const { return m_anonymous; }
+
+    Inode* inode() { return m_inode.ptr(); }
+    const Inode* inode() const { return m_inode.ptr(); }
+    size_t inode_offset() const { return m_inode_offset; }
+
+    String name() const { return m_name; }
+    void set_name(const String& name) { m_name = name; }
+
+    size_t page_count() const { return m_size / PAGE_SIZE; }
+    const Vector<RetainPtr<PhysicalPage>>& physical_pages() const { return m_physical_pages; }
+    Vector<RetainPtr<PhysicalPage>>& physical_pages() { return m_physical_pages; }
+
+    void inode_contents_changed(Badge<Inode>, off_t, ssize_t, const byte*);
+    void inode_size_changed(Badge<Inode>, size_t old_size, size_t new_size);
+
+    size_t size() const { return m_size; }
+
+private:
+    VMObject(RetainPtr<Inode>&&);
+    explicit VMObject(VMObject&);
+    explicit VMObject(size_t);
+    VMObject(PhysicalAddress, size_t);
+
+    template<typename Callback> void for_each_region(Callback);
+
+    String m_name;
+    bool m_anonymous { false };
+    off_t m_inode_offset { 0 };
+    size_t m_size { 0 };
+    bool m_allow_cpu_caching { true };
+    RetainPtr<Inode> m_inode;
+    Vector<RetainPtr<PhysicalPage>> m_physical_pages;
+    Lock m_paging_lock;
+};