fix(surfnet): terminates the cli program on sigterm

[0xzrf]

Summery

Stops the surfpool surnet execution immediately after calling the SIGTERM

Changes

Added termination feature to the ctrlc crate, which signals the ctrlc:: set_handler to call the SimnetCommand::Terminate(None); on SIGTERM signal

Closes #514

[MicaiahReid]

@0xzrf were you able to successfully test this? I built and ran this branch, but SIGTERM didn't seem to do anything

[0xzrf]

@MicaiahReid umm, It does seem to run in my end.
I tested it by running the following:

kill -15 <PID>

[MicaiahReid]

@MicaiahReid umm, It does seem to run in my end. I tested it by running the following:

kill -15 <PID>

Hmm, I'm on macos and that's not working for me 🤔