Proxy: Construct pchan hash when syncing armature proxy

This makes bone lookup much faster (by avoiding liner string lookup)
and speeds up depsgraph construction time on file open.

source/blender/blenkernel/intern/armature.c

@@ -1781,6 +1781,7 @@ static void pose_proxy_synchronize(Object *ob, Object *from, int layer_protected
 	BLI_duplicatelist(&pose->agroups, &frompose->agroups);
 	pose->active_group = frompose->active_group;
 
+	BKE_pose_channels_hash_make(frompose);
 	for (pchan = pose->chanbase.first; pchan; pchan = pchan->next) {
 		pchanp = BKE_pose_channel_find_name(frompose, pchan->name);