Consider using a separate session for every child process

[gsalgado]

Currently, every process we start is on the same process group as the parent process, and that means a Ctrl-C in the terminal will cause a SIGINT to be sent to every process we start, but our parent process also has logic to detect a SIGINT and forward it to every child, so by default every child ends up receiving two SIGINTs, unless one adds a start_new_session=True item to open_in_process()s subprocess_kwargs` dict, like we do in trinity

As Piper suggested, though, we might want to have that as the default behaviour here

[pipermerriam]

Can we even go as far as detecting this property of the child process and disabling the SIGINT behavior in the cases where the child process gets it automatically?