Figure out a minimal healthcheck pattern

Some of our examples use a healthcheck which relies on the admin endpoint, and uses `curl` to check readiness

Ideally we want a really minimal healthcheck that requires little/no container/system tools to check, that we could include in the published images - adding curl/nc in the distroless container is not trivial/desirable

One way of doing this would be if there were a filesystem file that could be checked for. This would definitely be the ideal

Another possibility - which would still require admin and a util - would be to expose admin only on a unix socket and connect to that with `socat`

I have a current need for something like this - but there is also a recent ticket related to this - #31614