Fix T71908: Animated properties are lost after frame-post handler

The issue was caused by special handling of animation update after
manual edits in frame_post handler: to avid loss of manual edits
done on top of animated property. This was done as a separate pass
for non-animation update after frame_post did modifications.

This caused some other side-effect: non-modified animated property
was re-setting to the value which is used in the viewport.

Idea of this solution is simple: preserve values which came from
animation update through copy-on-write process. The actual process
of this is a bit involved: need to decode RNA path and do it twice
since f-curve might point to a sub-data which pointer will change.
Since this is only done for non-active depsgraph (aka depsgraph
used for render pipeline) this is probably fine since all this
extra overhead is just a fraction of overall render process.

Differential Revision: https://developer.blender.org/D6330

source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.h

@@ -25,6 +25,7 @@
 
 #include "DNA_ID.h"
 
+#include "intern/eval/deg_eval_runtime_backup_animation.h"
 #include "intern/eval/deg_eval_runtime_backup_movieclip.h"
 #include "intern/eval/deg_eval_runtime_backup_object.h"
 #include "intern/eval/deg_eval_runtime_backup_scene.h"
@@ -44,6 +45,7 @@ class RuntimeBackup {
   /* Restore fields to the given ID. */
   void restore_to_id(ID *id);
 
+  AnimationBackup animation_backup;
   SceneBackup scene_backup;
   SoundBackup sound_backup;
   ObjectRuntimeBackup object_backup;