Fix incorrect exitcode in SIGTERM and SIGINT.

[asdacap]

• Long overdue fix on incorrect exit code on sigterm/sigint.
• On POSIX, when given SIGTERM/SIGINT, the application should exit with a specific exit code instead of 0.
• Without this, a script may not behave as expected. For example, if I have a script something like this, which sync, then remove the directory then sync again, on the first nethermind run, when I ctrl-c, I would expect it to stop the whole script. Instead, it remove the directory and start the second run.

nethermind --Sync.ExitOnSynced true
rm -rf thedir
nethermind --Sync.ExitOnSynced true

Changes

• Return proper exit code.
• Also consolidate the various exit signal.

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

Notes on testing

• On linux SIGTERM: ✔️
• On linux SIGINT: ✔️
• On mac SIGTERM: ✔️
• On windows: ✔️
• Exit after sync should have code 0: ✔️

[rubo]

Are there any implications because of this change?

[asdacap]

I'm guessing its a bit spower compared to kestral. Metrics seems to still works.

[benaadams]

It disables non system grafana metrics for Windows 😢

As it uses HttpListener and you need to explicitly give it permissions (outside in OS) to listen on that port or run in Admin mode.

Perhaps switch on OS as I assume Windows isn't paying attention to SIGTERM?

[benaadams]

#6326