UV Sculpt: Rename strength_curve and curve_preset

Similar to 327a1925cf

* Renames `strength_curve` to `curve_distance_falloff`
* Renames `curve_preset` to `curve_distance_falloff_preset`

These changes are done for consistency with the other concepts in the
other paint modes.

Pull Request: https://projects.blender.org/blender/blender/pulls/147071

scripts/startup/bl_ui/space_image.py

@@ -1415,7 +1415,7 @@ class IMAGE_PT_uv_sculpt_curve(Panel):
 
         if props.curve_distance_falloff_preset == 'CUSTOM':
             col = layout.column()
-            col.template_curve_mapping(props, "strength_curve")
+            col.template_curve_mapping(props, "curve_distance_falloff")
 
 
 # Only a popover.