This replaces `uiItemFullOMenuHold_ptr`, `uiItemFullR_with_popover`,
`uiItemFullR_with_menu`, `uiItemPopoverPanel`* and `uiItemSpacer` API
with methods following uiLayout refactors and the Python API.
Part of: #117604
Pull Request: https://projects.blender.org/blender/blender/pulls/141050