Fix stop succeeding when instance isn't stopped

[Sploder12]

resolves #2907

When running stop on an instance that could not be stopped no error would be reported. This was because QemuVirtualMachine::shutdown(force=false) ignored the result of vm_process->wait_for_finished(shutdown_timeout) which indicates if a timeout occurred or not. This issue does not seem to be present in other VM backends.

This PR makes it so the timeout is not ignored and the timeout is properly reported.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.94%. Comparing base (0189211) to head (dd7cfb0).
Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3684      +/-   ##
==========================================
+ Coverage   88.92%   88.94%   +0.02%     
==========================================
  Files         254      254              
  Lines       14271    14276       +5     
==========================================
+ Hits        12690    12698       +8     
+ Misses       1581     1578       -3     

Flag	Coverage Δ
	88.94% <100.00%> (?)

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[ricab]

Hey @Sploder12, thanks! Would you mind rebasing? Although there doesn't seem to be a conflict, GH still shows a diff to the old version here:

[andrei-toterman]

You could look into our MP_EXPECT_THROW_THAT macro, which we use to add a matcher for the exception message, so that it's more clear about what you actually expect, not just any random std::runtime_error.

[andrei-toterman]

Alright, code looks good and now the stop command fails as it should. Thanks, @Sploder12!