- That restores capturing output from external processes and printing
segfaults to the console.
- Also, fix test_print_faulthandler because it started to fail due to
env activation for the default env.

- That allows to show our kernel error message in every client connected
to a conda environment that didn't start.
- Also, update comment in test_kernel_crash accordingly.

This fixes loading the project's session files or the ones in the
previous session if a console was left in debugging mode.

This prevents freezes when closing Spyder and either a kernel restart or
closing a client is requested while debugging.

That's not really necessary because the plugin declares the same method,
so it was being called twice when the main window is closed.