Add option `--execute` to `lean research`

It would be great if we could execute the cells of research.ipynb from the terminal using a command like
lean research <project> --execute.

Note, this feature is already available for Jupyter notebooks. You can run the command
jupyter nbconvert --to notebook --inplace --execute research.ipynb
or alternatively you can use papermill.

But it doesn't work that way in connection with Lean CLI as the notebook is running in a Docker container.

Bonus
Ability to execute cloud research notebooks, i.e. something like
lean cloud research <project> --execute.

Motivation
I use the research environment frequently to create customized reports/charts and this feature would be helpful to automate that process.

Start at the lean research <project> CLI entry point and review how research.ipynb runs inside the Docker container. Compare the requested behavior with jupyter nbconvert --to notebook --inplace --execute and papermill; done means local research notebooks execute through --execute, with cloud execution treated as the stated bonus scope.