This replaces uiItemMContents, uiItemDecoratorR* and
uiItemProgressIndicator API with uiLayout methods following
uiLayout refactors and the Python API.
`eButProgressType` is changed to a typed enum class
`blender::ui::ButProgressType`
Part of: #117604
Pull Request: https://projects.blender.org/blender/blender/pulls/141189