a017a6cc54
This converts the public `uiItemO` function to an object oriented API (`uiLayout::op`). Also this rearranges `idname` paramether, since this the only one required, and to make format similar to `uiItemFullO` Note: One of the benefits of moving from a public function to class method is to reduce API usage difference between C++ and Python. In Python this method is called `UILayout::operator`, however `operator` is a reserved keyword in C++. Part of: #117604 Pull Request: https://projects.blender.org/blender/blender/pulls/138776