Run R cells in vscode using jupyter

When executing a {python} cell in vscode it automatically starts a jupyter kernel and console.
When executing a {r} cell, it instead relies on the vscode R extension to start a console.
I would prefer R cells to be executed via jupyter as well, using an R kernel.

This is mostly for two reasons:

• The jupyter extension makes it really easy to work with different virtual environments. I can simply add a different kernel for each environment. I haven't found a way of specifying a virtual R environment in the vscode R extension except for manually setting paths in the configuration.
• the jupyter console looks and feels much nicer (even compared to radian) and I'm more used to it.

The issue names no files or tests. Start by tracing VS Code cell execution and the existing Jupyter and R-extension integrations; done means R cells launch through a Jupyter R kernel and allow the environment or kernel selection described in the issue.