"install python" option from kernel picker doesn't lead to obvious next step

[amunger]

Testing #16577

1. create a dev container with a definition that isn't python focused (I used c# .net).
2. try to run a cell in a notebook and select "python environment" -> "install python"
3. click download and install from the popup

🐛 nothing is downloaded or installed AFIACT
🐛 python walkthrough opens, but not to the "install python" step, and I'm not really informed that I need to do it myself

If python isn't installed, or isn't found by the environments extension, clicking "install python" from the kernel picker will show a notification

[DonJayamanne]

We execute the python command python.installPython
Transferring to Python extension

[eleanorjboyd]

depends on this change first I think: #24963