vm: refactor page_array and functions into a separate source file

vm/model.c

@@ -0,0 +1,13 @@
+#include <socks/vm.h>
+
+static vm_model_t model;
+
+vm_model_t vm_memory_model(void)
+{
+	return model;
+}
+
+void vm_set_memory_model(vm_model_t m)
+{
+	model = m;
+}