[Client] Make client accept ctrl-c and exit safely (ie with no transactions mid push, or unwritten)

[mickvandijke]

The CLI app should gracefully exit when receiving the SIGINT (ctrl_c) signal. That means that important operations in action should either finish to completion or do a cleanup before exiting.

[mickvandijke]

Issue stalled. I really can not figure it out without major refactors. My idea was to spawn a new Tokio task for each command and awaiting gracefully in the main thread when receiving the ctrl_c signal using Tokio select. Unfortunately, the Opt struct contained several fields that do not implement Send, which makes it difficult to share it between threads.

Unassigned myself for now so that someone else could pick it up.

[happybeing]

I'd like to add that this would also apply to third party clients using the Autonomi API, so any measures should be able to be applied to any app using the APIs.