Isomorphic IInstaller: Support installing dependencies with the debugger

With PR: https://github.com/microsoft/vscode-jupyter/pull/10604 we realized that to have an isomorphic dependency installer we will need to use the debugger.

We have a dependency installer that has a nicer user experience, which is the IInstaller. If we were to implement an isomorphic installer, we would both use the debugger and IInstaller.

An important point to consider is that the code below does not work with the debugger:

// TODO: Installing pandas does not work with the debugger.
// It takes a long time, then it breaks with:
// error: Command \"clang -Wno-unused-result -Wsign-compare -Wunreachable-code...
export const debuggerInstallPandas = [
    'import subprocess as _VSCODE_subprocess',
    'import sys as _VSCODE_sys',
    `def _VSCODE_install_pandas():
  _VSCODE_subprocess.check_call([_VSCODE_sys.executable, "-m", "pip", "install", "pandas"])`,
    '_VSCODE_install_pandas()',
    'del _VSCODE_subprocess, _VSCODE_sys, _VSCODE_install_pandas'
];

To correctly implement the isomorphic installer, we might need to study how %pip and %conda are implemented on Jupyter.

[DonJayamanne]

It’s frozen. So you need to eval some code from the debugger.

Aah yes, you’re right, forgot about that one (thought that only applies to debugging remote kernels, but not a consistent experience if we don’t support remote).

[rchiodo]

Even with an IKernel, if you’re debugging a cell or debugging the IW, you can’t use the kernel to do the install. It’s frozen. So you need to eval some code from the debugger.

Maybe we just skip installing when debugging then. Although I think the install magics wouldn’t be very hard to call: https://github.com/ipython/ipython/blob/0f4a73c91db71cde174275337fc5e226acc9dd7d/IPython/core/magics/packaging.py