vh yaml step notebook.ipynb doesn't work with the new papermill

[JuhaKiili]

We are moving to the new Papermill in the Jupyhai so Valohai CLI does the same.

Today you can generate step with vh yaml step hello.ipynb

The YAML generating code for a notebook is also duplicated in two places (Jupyhai, Valohai-CLI).

• [ ] Move command generation code to valohai-utils
• [ ] Make valohai-cli and jupyhai use that code