Anim: avoid 'unshare' node for custom properties and shapekey values

When creating depsgraph relationships for drivers, avoid creating the
'unshare' depsgraph node for drivers on custom properties and on
shapekey `value` properties.

This should fix a significant part of the performance regression
mentioned in #140706.

Pull Request: https://projects.blender.org/blender/blender/pulls/140724

source/blender/depsgraph/intern/builder/deg_builder_relations_drivers.cc

@@ -245,12 +245,26 @@ bool data_path_maybe_shared(const ID &id, const StringRef data_path)
   /* As it is hard to generally detect implicit sharing, this is implemented as
    * a 'known to not share' list. */
 
+  /* Allow concurrent writes to custom properties. #140706 shows that this
+   * shouldn't be a problem in practice. */
+  if (data_path.startswith("[\"") && data_path.endswith("\"]")) {
+    return false;
+  }
+
   if (GS(id.name) == ID_OB) {
     const Object &ob = *reinterpret_cast<const Object *>(&id);
     const bool is_thread_safe = (ob.type == OB_ARMATURE && data_path.startswith("pose.bones["));
     return !is_thread_safe;
   }
 
+  /* Allow concurrent writes to shapekey values. #140706 shows that this
+   * shouldn't be a problem in practice. */
+  if (GS(id.name) == ID_KE) {
+    const bool is_thread_safe = data_path.startswith("key_blocks[") &&
+                                data_path.endswith("].value");
+    return !is_thread_safe;
+  }
+
   return true;
 }