feat(relay): Exit container on healthcheck failure

[aminvakil]

Another attempt of fixing getsentry/sentry#109002 after #5750.

docker-compose does not restart services if they become unhealthy for any reason whether it's web container not accessible and returning NXDOMAIN or any another reason, this PR adds a kill signal to PID 1 to healthcheck failures which can be enabled using kill-on-fail argument, effectively stopping container, and as restart_policy is unless-stopped in self-hosted, it should restart itself.

This may rises a problem of getting relay in a restart loop if it does not get healthy, which is fine IMO.

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[aminvakil]

There is a failure on building it, I should add deps to it, will make ready for review afterwards.

[aminvakil]

It's working correctly as expected , but what about having flush-dns-on-fail instead of kill-on-fail?

This is better I think, it seems relay handles SIGTERM perfectly well.

[aminvakil]

cc @aldy505

[aldy505]

Makes sense to me