Implement c/r error reporting

[kolyshkin]

Currently, when checkpoint or restore fails, runc diagnostics is inadequate, as the error itself is hiding in criu logs. This is why we have something like

		grep -B 5 Error "$workdir"/*.log ./image-dir/*.log || true

all across the https://github.com/opencontainers/runc/blob/main/tests/integration/checkpoint.bats

Perhaps we can implement something like this in runc itself, so it will show something useful in case of error.

[danishprakash]

@kolyshkin mind If I take a look at this?

[kolyshkin]

Fixed by #3816

[kolyshkin]

Somehow I forgot the last step, here it is: #4251