refactor: shutdown signaling in ping-pong

[hopeyen]

Description

• Trying out the simplest workflow of shutdown signaling control for mutli-thread in the ping-pong example's context. The similar workflow can be used in other radios along with more considerations such as http service, metric port, and/or db connection.
• Refactored register_handler and message channel sender into sdk such that a WakuMessage mpsc is required and thus register_handler becomes generic and can be automatically called when initiating a Graphcast agent.
• Need to increment SDK's minor version

Issue link (if applicable)

Part of https://github.com/graphops/engineering-meta/issues/43

Checklist

• Are tests up-to-date with the new changes? (no unit tests, can add in e2e)
• Are docs up-to-date with the new changes? (update ping-pong tutorial)

[axiomatic-aardvark]

It's kind of hard to test this when waku-org/waku-rust-bindings#66 is not resolved since it often causes early shutdown of the Radio.

Overall it looks like it's working, if the Radio starts running properly and I do ctrl+c it does shut everything down. Although sometimes there's a large interval between clicking ctrl+c and the actual shut down (something like 30 seconds). Also the logs keep going after the "Shutting down" log:

So to recap - sometimes it shuts down fast, sometimes it takes a while and the logs keep going, then it shuts down.

Something weird also happens sometimes when there's a panic (from the 'sni' issue)

I click ctrl+c but it doesn't to anything and I have to close the terminal.

Again - sometimes it panics and shuts down, other times it gets stuck.

Overall it's still a great improvement though! The main purpose of the PR (to make the program stop after a shutdown signal) is delivered, I think it can go in and we can have a new Issue to tackle why it sometimes doesn't shut down when there's a panic, and one for the sometimes observed delay + logs that keep going after a shutdown signal, before the actual shutdown. Up to you, either that or those two things can be tackled as part of this PR.

[hopeyen]

Thanks for the review. That sounds good, I will let this one set for a bit and open up a different PR for updating the waku rust binding version and see if that fixes the 'sni' issue for the radios to not panic from that

[hopeyen]

While issue sni gets fixed in dependency, I've added a force shutdown that allows 5 seconds of wait time for graceful shutdown for ping-pong example; can be adjusted for specific radios

[axiomatic-aardvark]

timeout works perfectly