Cleanup: Rename original curve object type enum

This commit renames enums related the "Curve" object type and ID type
to add `_LEGACY` to the end. The idea is to make our aspirations clearer
in the code and to avoid ambiguities between `CURVE` and `CURVES`.

Ref T95355

To summarize for the record, the plans are:
- In the short/medium term, replace the `Curve` object data type with
 `Curves`
- In the longer term (no immediate plans), use a proper data block for
  3D text and surfaces.

Differential Revision: https://developer.blender.org/D14114

source/blender/editors/space_node/node_context_path.cc

@@ -47,7 +47,7 @@ static void context_path_add_object_data(Vector<ui::ContextPathItem> &path, Obje
     Light *light = (Light *)object.data;
     ui::context_path_add_generic(path, RNA_Light, light);
   }
-  if (ELEM(object.type, OB_CURVE, OB_FONT, OB_SURF) && object.data) {
+  if (ELEM(object.type, OB_CURVES_LEGACY, OB_FONT, OB_SURF) && object.data) {
     Curve *curve = (Curve *)object.data;
     ui::context_path_add_generic(path, RNA_Curve, curve);
   }