setup jupyter notebook root folder

[prudhomm]

I'm not sure this line should stay here : if the preset selected is not python there is no reason this path should be correct.
The advantage of this setting it that when we run a notebook in vscode, it automatically find the development packages installed in build directory, so there is no need to set by hand $PYTHONPATH.
The drawback is that when we launch a kernel, the working directory is no longer the directory where the ipynb file is saved, it is the one set in this line. So it is messy to load the config file (for example in python/pyfeelpp-mor/feelpp/mor/nirb/test_nirb_offline.ipynb, the path is hard coded to a local path "/home/saigre/Documents/code/feelpp/python/pyfeelpp-mor/feelpp/mor/nirb/model/square/square.cfg" which should have not been pushed, my bad !)

see eg:

"jupyter.notebookFileRoot": "${workspaceFolder}/build/python/install/lib/python3/dist-packages",

I don't know what would be the best way to set the environment easily : automatically set PYTHONPATH to the install directory, while the working directory still being the one where the notebook file is saved...

Originally posted by @thomas-saigre in #1944 (comment)

• add support for testing notebook using pytest and ctest #2054

[prudhomm]

I have a solution to propose that does not directly involve vscode but rather cmake and the presets.
I propose to start our notebooks like this:

import sys,os
dev_mode=True
preset='python'
if dev_mode and os.path.exists(f'../../build/{preset}/install/lib/python3/dist-packages'):
    sys.path.insert(0,os.path.abspath(f'../../build/{preset}/install/lib/python3/dist-packages'))
    print(sys.path)

it is the choice of the user to select the dev_node or the preset.
it works nicely.
I am adding notebooks to python and some automated pytests for them.