Add ProcessExitGroup to ensure children are killed on exit

[fasmat]

Motivation

If the node exits unexpectedly or is killed with SIGKILL instead of SIGTERM it will not kill post services that it spawned.

This PR fixes this by adding a job object that kills processes assigned to it on close. For information on how this works see the official Microsoft documentation on job objects: https://learn.microsoft.com/en-us/windows/win32/api/jobapi2/nf-jobapi2-assignprocesstojobobject and https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-jobobject_basic_limit_information

Changes

• On windows ProcessExitGroup adds the new process to a job object (itself) and ensures that they are closed when itself is closed
• On other systems the ProcessExitGroup only ensures that new processes are in the same process group as the main process.

For windows this ensures that if the main process crashes / is killed all commands started through the ProcessExitGroup will be killed as well. On other systems this is only true for crashes. Killing the node with kill -9 will not cause the child processes to exit automatically. For this they have to listen to signals about their parent and close themselves.

Test Plan

• n/a

TODO

• Explain motivation or link existing issue(s)
• Test changes and document test plan
• Update documentation as needed
• Update changelog as needed

[poszu]

Would it make sense to add a unit test that would:

1. spawn process A that spawns process B
2. kill process A
3. observe that process B died

[poszu]

How about making it all private?

[fasmat]

wdym? These methods need to be called from outside the object?

[poszu]

But it's used in the same package, isn't it?

[fasmat]

Would it make sense to add a unit test that would:

1. spawn process A that spawns process B
2. kill process A
3. observe that process B died

wouldn't work on linux (because the code actually doesn't work on non-windows systems)

[poszu]

Would it make sense to add a unit test that would:

1. spawn process A that spawns process B
2. kill process A
3. observe that process B died

wouldn't work on linux (because the code actually doesn't work on non-windows systems)

I think it's fine to test windows-specific code only on windows :) Just skip/don't compile the test on a different OS.

I realize that the test would be much longer than the implementation, but on the other hand, the code for it is cryptic and prone to regressions :(

[poszu]

This shouldn't be required with spacemeshos/post-rs#141.

[fasmat]

Superseded by #5201