Make moving the cursor in UV Editor a 2d edit transform

This flags moving the cursor in the Image Editor T_2D_EDIT with the
following benefits:

- dissallowing e.g. Z constraints
- improving the header display:
-- it should not use scene units
-- now respects if we are moving in pixel coords or not

part of upcoming fix for T86796
ref D10817

source/blender/editors/transform/transform_convert.c

@@ -1187,10 +1187,11 @@ static eTFlag flags_from_data_type(eTConvertType data_type)
       return T_EDIT;
     case TC_MESH_UV:
       return T_EDIT | T_POINTS | T_2D_EDIT;
+    case TC_CURSOR_IMAGE:
+      return T_2D_EDIT;
     case TC_PARTICLE_VERTS:
       return T_POINTS;
     case TC_POSE:
-    case TC_CURSOR_IMAGE:
     case TC_CURSOR_VIEW3D:
     case TC_OBJECT:
     case TC_OBJECT_TEXSPACE: